I understand your point.
Why absolutely trust people that don’t provide you (for a not well known reason) the odds to receive the big price? Is a nonsense.
It’s a really good reason to not trust them at all.
And people who said “they have no reason to play dirty on us!” are really cute.
Actually there’s a really good reason called money.
But don’t fool yourself, there’s absolutely anything to investigating for.
You pay for gems and receive exactly for what you pay. What you do with that gems is not a law issue.
You can accuse them to be morally questionable and profeeters, but not criminals.