Loosegrown so cheap! any alternatives?

[echelon6]

I've been out of the space for 2 decades. I want to buy something again, and I've been checking out LGD. I remember paying 15k usd in 2006 for a F SI1 1.6ct (AGS000 back in the day). Today, on LGD the same stats can be bought for 500usd. Absolutely amazing. Any alternatives to LGD so I can properly shop around? The usual vendors like James Allen etc seem to charge triple what LGD charges for the same stats, can someone help me understand the reason behind this? I don't mind paying more, but I need to understand why.