It’s sooo easy to get ripped off in the diamond trade business unless you’re dealing in Museum quality diamonds of 1 carat or more and know what you’re doing. D,P, IF.
Take a semester of Gem grading and then hit the gem merchants in Miami. You’ll be astonished at how many poorly grade diamonds are sold well above their value.
That's the nature of any commodity business. The dealer has to make his money, which means the market bid on your object is always less than the market offer.