0.75 to 1.25 is a HUGE size range.
A 0.75 ct diamond will sit differently in a setting than a 1.25 ct one will. Just because a random jeweler or sales associate at a jewelry shop says you can get away with putting this size range into a setting does not mean that you should necessarily do it.
You've already stated that you haven't been happy with their honesty in what they are trying to sell you... "Boggles my mind that every jeweler I’ve talked to has tried to sell me a $2000 stone for $6000."
Learnt that lesson today. Wish I found this site sooner.