Older GIA certification

[chrono]

Nice thorough guidelines for face to face dealings. I am putting together online options to have in case face-to-face does not pan out.

You mention credit card. So would you not advise the online "bank wire" or "cashier check" options and in person, I assume you would reject "cash" or "cashier check" better prices. Is this due to reduce risk of fraud??

For vendors that I've dealt with and trust, I have no issues with bank wire. If it is an unknown vendor, paying using CC affords you more protection should you need to return the stone to get a refund.

 

[kb1gra]

denverappraiser - I promise that I never assumed I could purchase from the Rapnet. I was just assuming that having the numbers (that is is not clear if I would see anyhow) would help me sort out whether a diamond under consideration is at an appropriate price. Unlike online, I get the impression that buying diamonds in person is a lot like buying a car. The seller starts at a number that is not the lowest number they will actually sell the stone at. I find that stressful and confusing. (I hate buying cars for that reason) I hate questioning a person's price so I feel like I need a way to gauge whether is is appropriate for me to question the price rather than badgering some poor vendor who is actually selling at a good price. Hopefully you see what I am struggling to figure out and if you have any thoughts of your own to share that would be great.

Wink and Rock Diamond - I am enjoying your discussions.

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

This restores the fundamental question of "what is fair?"

The answer to that question is "priced competitively with others in the market."

It really has nothing to do with what the vendor paid for it, truly. And as pointed out - Rap actually tells you nothing about that anyway.

The only way to decide if you are paying a fair price is to find similar stones (as close as you possibly can on all counts) and see what the asking price is for them. If you can't find another stone for a better price - then I guess you did okay, didn't you? And if you do find a better price, why is it better? Does that stone have a less desireable inclusion? a tint that is more brown than yellow? a cut that doesn't quite meet the mark but is still good? There's too many variables here to determine what is "fair" and plenty of resources for you to make that decision for yourself.

But there's no document out there where you input 1.05 g/vs2 AGS0 and out spits "you should pay $X and not a cent more!"

It's not like kelley blue book - which even then, has zero value, because an item for sale is worth what someone will buy it for, no more, no less.

 

[denverappraiser]

You mention credit card. So would you not advise the online "bank wire" or "cashier check" options and in person, I assume you would reject "cash" or "cashier check" better prices. Is this due to reduce risk of fraud??

Yes.
Most people don't do this very often. You are usually dealing with a stranger and chances are good you're not all that confident in you own skills to understand the variables. The credit card typically costs about 2% of the transaction price and it's relatively cheap insurance that everyone will be on the up and up if something goes south. If you ARE familiar with the dealer, or you are yourself an expert, by all means take the discount and keep the money.

 

[adom]

kb1gra - great perspective - thanks

denverappraiser - certain online vendors, like WF and BG, offer a wire discount. If, in the end, that is the chosen route, would you opt for their wire discount?

 

[chrono]

kb1gra - great perspective - thanks

denverappraiser - certain online vendors, like WF and BG, offer a wire discount. If, in the end, that is the chosen route, would you opt for their wire discount?

For WF and BGD, I have no issues with doing a wire transfer.

 

[adom]

^ thanks

 

[WinkHPD]

I rarely disagree with Denver Appraiser, but we work on extremely thin margins in the diamond world.

I have found cc costs an average of 3.25 % depending on the card used and the amount of "free" benefits the cc company is giving you at our expense. Cash back cards can cost up to 5% for the seller and we are not allowed to tack that on to the cost of taking your card. There are actually over 400 different rates that a cc company can charge based on what the freebies are and the "risk factor" that the cc company decides to sting the vendor with for being an Internet vendor. It was confusing enough when there were only 200 or so. The credit card companies are all like, "Hey, the merchants pay it all and it is free to the consumer, so why make the cost transparent to the vendors..." They keep coming up with more ways to give the consumers free things and we merchants are expected to grin and bare it.

In addition, some of the companies now allow you up to a year to holler, "calf rope" and get your money back. Credit cards are a nightmare to us on the margins that we work on, and one fraudulent sale could take us a LONG time to recover from.

Thanks, but no thanks. To counter this, most of us offer wire transfer discounts. You can easily google a vendor to see if that vendor has EVER had a complaint about not returning every penny owed on a return. If yes, move on. If the vendor is a Pricescope sponsoring vendor, you can be very sure that vendor has been vetted by the Pricescope leadership team and will continually expected to live up to their obligations to remain a Pricescope sponsor.

Just my opinions on the joy of taking credit cards, and yes, I buy everything that I can for my business on a miles card and enjoy that side of the equation.

Wink

 

[adom]

wink - That all makes complete sense. Thanks as always.

 

[Rockdiamond]

Wow, turns out there were a lot more responses than the drinking one. My bad!

Ok…..

RockDiamond – Nice of you to check on what I could buy from RAP. Notice I have yet to rush into that purchase. Interesting comments on ASET and store differences and such. In case I have not mentioned it above, as I currently understand it, the hope is to find the stone at a gem show. This is part of why I am thinking I am putting together a “kit”. Bring my own stuff and be able to compare apples to apples as we go around. Lastly, so where are theses active links. Don’t see them or am I just dumb?

Wink – Great description of stone cut behaviors. I did see a very interesting youtube demonstration of two similar diameter stones in bright vs low light. One ot the stones shrank measurably. It was shocking. How do you replicate that in a setting that will have lights everywhere!

Denverappraiser – Maybe the demo I saw utilized the trading platform that won’t be available to me. It was a search page that showed individual stones and something about their prices and % back for that particular stone. Was that the platform? Can you tell me how you might approach making sure that a diamond you were considering buying was at a fair price. Do I want to “cheat” a seller? Never. But I don’t want to get robbed either. This is so different from ordinary daily shopping. ☹

HI Adom,
I missed this post earlier.
Let me ask you- what is the goal of buying at a gem show?
The reason I ask is that you may be giving up some valuable benefits.
First of all- even though it's been brought up that many jewelry stores have ultra bright lighting that might be deceptive, bright lights are absolutely necessary to make gemological examinations. Conditions are trade shows are rarely as conducive to a good examination.

If lowest price is the goal- use the PS diamond search function and pick the lowest priced stone- you're not going to find prices much cheaper- if at all- at a gem show, and you'd be far less likely to get a safe sale- which includes a money back guarantee.

By all means- go to the Gem show- have fun!

But leave your wallet home

 

[Rockdiamond]

HI All,
Wink- We happened to have AGSL000 stones that were part of the comparison. For viewing: we have some very bright areas as well as dark areas here in the office- and the client looked at the stones all over.
The stone I posted, which as I said- won't look great on ASET- looked very good in real life. In low lighting the stone performed comparably to the AGSL000 posted below of the same color and clarity.
One of the areas that you and I will not agree on is leakage, and it's benefits, and detriments.
Regardless, these stones were destined to be earrings- and as such there's different considerations in terms of what might be considered optimal light performance as compared to a stone which is going to be set into a ring.

This is one of the AGSL 000 stones. More PS friendly. But it was by no means super ideal. Even with AGSL000 there's variation.


You can see the smaller table ( 57%+-) in the picture. The two stones I've posted in this thread were within .02ct of each other, and both were in the 4.10+- ct range
The first stone, which I posted earlier in the thread had a 60%+- table- and spread 10.25mm average, while this stone, 000 AGSL spread 10.10mm average
These were each part of a matching pair, and when yu looked at a pair of 10.25's vs a pair of 10.1's the difference in size was noticeable. If we take the entire project into consideration, the greater spread came into play.
The client chose the larger pair. I can't say she was wrong. She wanted well cut- but super ideal was not something requested. More about bang for the buck
If it was for an engagement ring and she wanted a perfect cut, obviously I would not suggest any of these stones.
Again- the scope of the project, and purpose of the diamonds come into play.
Sacrificing a 2% difference in cut to get better size color and or clarity is sometimes a better choice in some cases

David,

I did not see the stones and do not know the numbers, but I will always acknowledge that AGS has some combinations that I do not agree with that are possible to receive AGS 0 cut grade. On the whole the AGS cut grade is vastly superior and more reliable than GIA EX. As for the exceptions, I do not buy, or sell, those either.

I have chosen in my business to be extremely snarky about what I will and will not sell. I could sell more, and much more easily if I did not kick so many pretty stones to the door, but then I would not be as proud of the diamonds that I do sell. It is my JOY and my MISSION in life to preach the gospel of fantastic cutting to all who will listen. When you preach to me the gospel of "good enough" it falls on deaf ears. Even if, as it appears in this case, it was what your customer wanted.

Good enough does not mean bad, just not worthy of the buy back and trade up policies that the top cut quality houses are able and willing to offer, since they know that their diamonds will always have the value to honor those policies.

I got my GG in 1975 and diamonds like I sell today were not even made then. I consider myself incredibly fortunate to have been in the industry while the great cutting revolution took place. The cutting changes forced the light scientists to study what was happening in the diamonds to understand why some diamonds looked so much better than others, and that research led to even more development in the quality of the cutting.

That the large cutters do not wish to make those changes is not at all surprising, after all, by cutting to heavier parameters a rough crystal can yield up to 6% or more than it would yield if cut to maximize beauty. With the artificial price bonuses that are paid for tiny increases of weight at certain sizes, it is no wonder that proper cutting is ignored by all but the most dedicated to absolute beauty. The financial payoffs are HUGE.

That is why there are 64,192 diamonds listed this morning on Rap.net from 1.00 ct to 1.05 ct and only 1,881 from 0.95 to 0.99. If I add only the barest of qualifiers to the search by asking for diamonds with 53 - 58 tables and 60 - 62 depths there are 5,413 diamonds in the 1.00 to 1.05 cts and ONLY 211 from 0.95 to 0.99. The other 1,670 0.95 to 0.99 ct diamonds were also cut for max weight and still could not make the magic number. (Only diamonds with AGS and GIA reports were searched for in all searches.)

To me this is a STUNNING revelation as to the horrible cutting that is used to meet or slightly exceed the magic one carat mark. With the first search I was seeing diamonds with 66% depths with only a cursory look at the list.

Sigh. Sorry. I get easily worked up when I see "stuff" like that listed for sale to the trade, knowing that it will soon be offered to anyone in the public without the knowledge to say, "Bye Bozo, I am going elsewhere with my money!"

Are there pretty diamonds that are good enough? I am sure there are. I just don't sell them or revel in them. One of the rewards for working hard enough to be successful is being able to sell only the very best and letting someone else have the sales that are not quite as well cut. It is working for me.

Wink

Hi Wink, knowing you as well as I do, I have zero doubt that you do in fact offer only the best to your clients- in your opinion.
That's the key phrase because we won;t share all opinions of what is the "best" in every case.
For example- I have seen well cut 60/60 stones which appear larger than an ideal cut of the exact same diameter- on many occasions. The lower crown, and larger table combine to make the stone look larger. It's possible that the ideal cut stone will have more contrast, resulting in brighter flashes- but many people feel the spread of the brilliance of a 60/60 appears brighter.

Also important to remember, 4ct diamonds have totally different considerations than 1ct diamonds. Both in light performance considerations, as well as market considerations.
The larger facets of the four carat can produce far more fire than the facets in a one carat stone, no matter how well cut the one carat stone.
And there's far less to choose from, as compared to one carat diamonds.
This presents different opportunities to judge stones of a given cut we might overlook if there was 10,000 stones on the market. Which is why I've looked at plenty of VG cut graded stones- and many of them were absolutely amazing.

If someone wanted to spend $60k on a four carat diamond, they can't buy an eye clean Super Ideal.
You might suggest they look at a smaller super ideal, maybe 3.2cts. But when you put the two stones next to each other, which is best?
The non super ideal will look immense next to the super ideal.
Maybe in a ring situation, for someone who also loved the increased contrast, the super ideal is best.
But if the person wants a pair of super large, and flashy earrings, the larger stone could easily be the "best" choice.

 

[Dancing Fire]

Easy, I'll pick a GIA XXX or a AGS 0 cut at 15% back of Rap...

I'm not sure if you're kidding or not but I'll assume not since this is the logic that is normally used.

420 of those 1047 stones are GIA/xxx. About half of THOSE are 15% back or more from Rap.

The next step would be, presumably, to filter based on fluorescence, HCA, dealer preferences, price, or some other criteria. My point is that knowing Rap has added nothing. Filtering directly from the 420 based on the other criteria will yield exactly the same results. The price that matters is the comparative price to those other 419 stones and other offers from different sources. Those are actual offers on actual stones. That's not just vastly more useful information for the task at hand, it's completely trumps the theoretical answer that's provided by Rap.

Neil
10 yrs ago I paid 25% back of Rap for a top cut 3ct GIA H&A stone.

 

[Dancing Fire]

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

IMO if a consumer can buy a top cut GIA/AGS H&A stone for 15%-20% back of Rap is a good deal.

 

[WinkHPD]

<SNIP>

Hi Wink, knowing you as well as I do, I have zero doubt that you do in fact offer only the best to your clients- in your opinion.
That's the key phrase because we won;t share all opinions of what is the "best" in every case.
For example- I have seen well cut 60/60 stones which appear larger than an ideal cut of the exact same diameter- on many occasions. The lower crown, and larger table combine to make the stone look larger. It's possible that the ideal cut stone will have more contrast, resulting in brighter flashes- but many people feel the spread of the brilliance of a 60/60 appears brighter.

At the cost of dispersion. I have never had a person chose a 60/60 when shown next to one of my diamonds. And I have never seen a 60/60 look “larger” through all light conditions. Even 60/60s of larger diameters can lose light at edges in soft light. Look at this image.



The diamond on the right has LARGER DIAMETER than the one on the left. In deceptive jewelers’ spotlights it does indeed look as large. But in normal lighting this is how it holds up against a superideal with edge to edge light return. By the way, this is a powerful tool seen live by clients.


Also important to remember, 4ct diamonds have totally different considerations than 1ct diamonds. Both in light performance considerations, as well as market considerations.
The larger facets of the four carat can produce far more fire than the facets in a one carat stone, no matter how well cut the one carat stone.
And there's far less to choose from, as compared to one carat diamonds.
This presents different opportunities to judge stones of a given cut we might overlook if there was 10,000 stones on the market. Which is why I've looked at plenty of VG cut graded stones- and many of them were absolutely amazing.

You said it yourself. We all have opinions. I shudder when I think of the VG diamonds I have seen, especially as carat weight increases. There is an amazing article showing how manufacturers of 2-3-4 carat diamonds swindle them to keep extra weight. I cannot link to the one I am thinking of, as it’s on my blog – but it’s also on at least one consumer protection website – and it has shocked the clients I have sent it to who have had read it... It uses real-life examples available for sale, showing what the yield SHOULD have been if the diamond was cut for consumer protection, versus what it was FORCED to be, in order to make a “magic weight” at 3 carats.

I would say the problem with a marginally cut 4ct diamond is the same as it is at any carats…maybe the fans are larger, but the imprecision still results in shattered internal reflections which are NOT as large as they could be, so you DON’T see all the fire and contrast you should were the diamond top-cut.

We are in the process of delivering a high 4-carat Cut To Order for one of my clients. This young man researched what we are talking about in-depth, including weeks in the diamond district, going to Tiffany, HOF, etc. He saw how profound the difference is between careful precision cutting – which is nearly impossible to find as you say – versus other stuff on the market. Sadly most people will never see a diamond cut like that. Thus, they are indeed limited in selection. And I admit you’re very correct about the dearth of options in higher carats, although I wish it were not so.

If someone wanted to spend $60k on a four carat diamond, they can't buy an eye clean Super Ideal.
You might suggest they look at a smaller super ideal, maybe 3.2cts. But when you put the two stones next to each other, which is best?
The non super ideal will look immense next to the super ideal.
Maybe in a ring situation, for someone who also loved the increased contrast, the super ideal is best.
But if the person wants a pair of super large, and flashy earrings, the larger stone could easily be the "best" choice.

Easiest answer of all. Look at those “60K” eye-clean 4-carat diamonds and recognize how many have a diameter smaller than 10.25mm. Now look at the ones meeting that diameter, but having a shallow crown, steep pavilion angles that will lose light, or other issues which prevent both the “edge to edge” brightness we discussed and ESPECIALLY which would limit and shatter internal reflections…

Now consider a diamond cut with high precision and ideal proportions to 3.60 carats. AMAZINGLY that diamond will actually measure physically AS BIG in diameter as many or most 4-carat diamonds, because they were forced to hold weight. And that 3.60ct top-cut will return light edge to edge so it actually looks bigger than those 4cts. And if it’s cut with precision the virtual facets will be undeniably larger than the forced 4ct diamonds.

And the punchline: A client will spend several thousand LESS for that well-cut 3.60, even though it may be the SAME PHYSICAL DIAMETER. And even when a bit smaller, the edge-to-edge brightness will make it look bigger, and the VF integrity makes it have superior fire and contrast! We see it all the time.

Wink

 

[Rockdiamond]

Two stones, exact same diameter, 60/60 on the left, Ideal on the right.
The 60/60 looks larger. No special lighting.
I could be mistaken, but I believe the photo you've used is stimulant, as opposed to real diamonds- like the ones in my picture.

In terms of VG cut grade diamonds, please come to visit!! The NY market allows us to look at a huge number of stones in varying qualities. There's PLENTY of amazing VG cut grade stones that lost the EX cut grade for aspects invisible to the naked eye.

About the 4ct stones we have been discussing- the stone I posted a picture of has a diameter averaging 10.25 mm and it is GLORIOUS in real life. The AGSL000 was 10.1mm average spread- noticeably and measurably smaller. The differences in light performance can not be measured in the same manner as the differences in spread. Differences in light performance perceptions are based on opinion. Not everyone will pick the same stone.
Maybe if we had an Ideal Cut stone of the same mm size it might have more fire. But it also might weigh 10% MORE, and come in at a higher per carat price. Even then it might not be preferred by a given client based solely on light performance.
Not everyone prefers the "Ideal" look- and all one need to do is read how many people right here on PS feel this way. Not everyone loves H&A patterns- many people prefer a more shattered light return because there's more scintillation.

I am extremely sensitive to swindled stones and size for the weight. The 4.00ct diamonds I've been using for examples in this thread were not close to the 4.00 mark. Not every stone that hits a .00 mark is necessarily a bad stone- although I agree, many are.
In my experience, Ideal cut stones spread smaller than well cut 60/60's. I honestly think some of this discussion s because we're thinking of different types of 60/60 cuts.
Even in your example you site stones with steeper pavilions which do not lend themselves to more spread for the weight.

If you can find some 3.60ct RBC's that spread 10.25mm, I'd be very interested to see them. I did find an AGSL 000 J/SI2 3 3/4 which would indeed cost quite a bit less than the 4ct J/SI2- the spread was 9.85mm average- a LOT smaller than the 10.25 average. The smaller stone might be a very good alternative for some buyers. Others will go for spread.
I'm not saying you- or anyone- is wrong to choose an Ideal Cut stone- just that I- and others- are not "wrong" in selecting different types of cuts.

I also have no doubt of your experience in what your clients prefer- but you must remember that you're an excellent ambassador for what you love- and your clients can't help but be infected by your enthusiasm.

 

[denverappraiser]

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

IMO if a consumer can buy a top cut GIA/AGS H&A stone for 15%-20% back of Rap is a good deal.

But I'm still not seeing how Rap helps. Why not filter the PS database for GIAxxx for the appropriate color/clarity/size, then sort for price, then subfilter for claims of H&A, fluorescence, HCA or whatever, and bias the results based on dealer preferences (if any)? That's what you're going to do anyway, isn't it? How does Rap help? It makes no difference if we're talking about R-5% or R-50%, it remains the same procedure and will end with the same conclusion. The issue is the comparison with the other actual offers on the table at the time. Knowing Rap hasn't helped a bit.

 

[denverappraiser]

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

IMO if a consumer can buy a top cut GIA/AGS H&A stone for 15%-20% back of Rap is a good deal.

But I'm still not seeing how Rap helps. After the Rap/discount filter, why not filter the PS database for GIAxxx for the appropriate color/clarity/size, then sort for price, then subfilter for claims of H&A, fluorescence, HCA or whatever, and bias the results based on dealer preferences (if any)? That's what you're going to do anyway, isn't it? How does starting with Rap help? It makes no difference if we're talking about R-5% or R-50%, it remains the same procedure and will end with the same conclusion. The issue is the comparison with the other actual offers on the table at the time. Knowing Rap hasn't helped a bit.

 

[Dancing Fire]

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

IMO if a consumer can buy a top cut GIA/AGS H&A stone for 15%-20% back of Rap is a good deal.

But I'm still not seeing how Rap helps. Why not filter the PS database for GIAxxx for the appropriate color/clarity/size, then sort for price, then subfilter for claims of H&A, fluorescence, HCA or whatever, and bias the results based on dealer preferences (if any)? That's what you're going to do anyway, isn't it? How does Rap help? It makes no difference if we're talking about R-5% or R-50%, it remains the same procedure and will end with the same conclusion. The issue is the comparison with the other actual offers on the table at the time. Knowing Rap hasn't helped a bit.

I'd rather pay 50% back then 5% back..

 

[LLJsmom]

With regard to the picture posted by Rockdiamond, the one on the right looks bigger to me. Am I nuts? Or is he referring to his left? I'm talking about the one where I can see the arrows. Thank you both Wink and Rockdiamond for posting these pictures. This is such an interesting discussion.

 

[Rockdiamond]

With regard to the picture posted by Rockdiamond, the one on the right looks bigger to me. Am I nuts? Or is he referring to his left? I'm talking about the one where I can see the arrows. Thank you both Wink and Rockdiamond for posting these pictures. This is such an interesting discussion.

HI LLJ- you're welcome and thank you for participating!
I did mean that the stone on the left looks bigger ( not that I don't sometimes confuse L&R, I am disclexic)
But your question is a very good one because it points out something which is integral to the discussion- perception.
To me the stone on the left ( no arrows) appears larger in the photo.
That you see it differently proves my point- perception will play a huge role in what we consider to be ideal light performance.

 

[Rockdiamond]

Dancing Fire - Are you suggesting that if I had a Rapsheet or Rapnet that you would consider 15% back a solid price for all top diamonds? Or was that only for that specific diamond description? How would you handle any other? i.e. H, slightly larger, eye clean VS2/SI1

IMO if a consumer can buy a top cut GIA/AGS H&A stone for 15%-20% back of Rap is a good deal.

But I'm still not seeing how Rap helps. Why not filter the PS database for GIAxxx for the appropriate color/clarity/size, then sort for price, then subfilter for claims of H&A, fluorescence, HCA or whatever, and bias the results based on dealer preferences (if any)? That's what you're going to do anyway, isn't it? How does Rap help? It makes no difference if we're talking about R-5% or R-50%, it remains the same procedure and will end with the same conclusion. The issue is the comparison with the other actual offers on the table at the time. Knowing Rap hasn't helped a bit.

I'd rather pay 50% back then 5% back..

DUH that makes total sense if it was the very same stone. The issue for buyers is that when look at a list of 10 G/SI1's and the lowest is priced 35% below the most expensive. Choosing the cheapest stone could easily be a mistake.

 

[denverappraiser]

DUH that makes total sense if it was the very same stone. The issue for buyers is that when look at a list of 10 G/SI1's and the lowest is priced 35% below the most expensive. Choosing the cheapest stone could easily be a mistake.

It's not even just that. If the goal is to buy the cheapest one, It'll still be the cheapest no matter what Rap says. Looking up Rap does no good and the Rap% doesn't make any difference. What actually matters is the price of the second cheapest and what the differences are, along with the differences with the other 418 supposedly identical stones.

 

[Rockdiamond]

DUH that makes total sense if it was the very same stone. The issue for buyers is that when look at a list of 10 G/SI1's and the lowest is priced 35% below the most expensive. Choosing the cheapest stone could easily be a mistake.

It's not even just that. If the goal is to buy the cheapest one, It'll still be the cheapest no matter what Rap says. Looking up Rap does no good and the Rap% doesn't make any difference. What actually matters is the price of the second cheapest and what the differences are, along with the differences with the other 418 supposedly identical stones.

Agreed-Rap price might be interesting to use for comparing pricing on different grades- and the implications on price in an overall sense. Interesting comparisons could be made comparing Rap to average selling price- seeing which types of stones trade closer to list.
But for any specific diamond being considered for purchase, percentage off rap in and of itself, is not the issue.
The bottom line is still that the stone needs to be evaluated on it's own merits in way a lab report can't convey. In some senses, the market does that fairly effectively. When I look at actual stones, the cheapest ones are usually that way for a reason.

DF- when a cutter tells me he's got GIA graded stones at 50 back, I know without looking that there's an issue.