Cannot help you with buying of gems. But -
If you know what you are buying and seller does not know - you can possible get a bargain. If you and seller both know the what is been sold - you will get it at real value ( +/ -). If you dont know what you are buying and seller does- then you will get ripped of. Works on anything you want to buy.
Thanks for the thoughts and comments, everyone. My wife uses a few well-known suppliers when she buys gems for her business. She does not typically buy off of e-bay. We have been to gem fairs in the US, including the Tuscon gem show. We know that when you buy from an established dealer, they will not lie to you because their reputation is at stake. Of course, we must decide if we like the quality. We look for inclusions, color, cut. But some things require sophisticated testing equipment that is not available outside of a lab. For that, you just trust that your seller is telling the truth. That's what I'm looking for in India: a seller whose reputation is important enough that they won't lie.
[ camelgirl: If you like the ring, you did not get ripped off! Buying for yourself is one thing. In our case, my wife would be buying wholesale, setting the stones in her own designs, and selling to the public. She has to know that the stones come from a trusted source because she does not want to rip off her customers (even unwittingly).
Thanks for the comments, everyone!
crvlvr: You have a good point about gems not being mined in India. However, it's possible and likely that many gems are still cut and polished in India. So even if the rough is imported from Thailand or Africa or wherever, there still might be good deals in India if they cut and polish there.!LCS, from what I understand that only the low quality or small size stones are cut in India by hand. and that is due to its lower labor costs. I suspect there might be more siphisticated methods of cutting bigger better stones elsewhere.