Dude. Rio Grande has craptons of diamonds from all over the place. Have done for 30 years. The difference between "what people pay" and "what jewelers pay" can be 95%.
Went to a rock'n'mineral show over the weekend. Every single person there had opals (of questionable quality, as per always) for the low-low-never-seen-before price of $20/ct. However, there was only one crew clever enough to put the damn things in glass display cases.
Everyone else was selling 1" pyrite crystals for $40. Put it in glass? $200.