My wife and I have been Ebay power sellers for many many years. She has been a GJG, GIA since 1995 and I have done lapidary related work in our business for more than 14 years, faceting only in the last four years.
Not all Ebay members are out to take advantage of the consumer, with ebay and gem rough I find through my own experience, that a piece of rough you win for $1.99 coming from Thailand is probably just that a piece of $1.99 rough.
Research the ebay gem rough sellers with the tools ebay offers and build a list of gem dealers to pursue more information about to put in your ebay trusted list. I personally do not purchase any rough on ebay from outside the United States only because there’s little recourse you have and then the hassle out ways the reward in that what was to be a great piece of rough. An another reason is, we travel regularly to and from these gem hubs and a mast majority of the reputable gem dealers over seas are not the ones you will most likely encounter on ebay. There is a filter on ebay to show just U.S. listings, send a message to the seller on an item your interested in and ask for their contact info, call them find out who they are, where they are, what is there return policy expectations truly not just the options that ebay allows for a seller, etc.
I believe a great source is your local gem and mineral clubs, join ask other members into faceting where they get there rough. Like Al said many of us here sell and have some sort of access to gem rough. All you have to do is ask! The annual Frolics are a good source, I believe that in the newsletters they post which dealers will be at the Frolics and many of them travel extensively through out the United States doing trade shows. Go through the members directory here on the USFG and many of us list if we sell gem rough.
Good gem rough is in high demand right now and prices are showing it.
Just my Opinion
The Gem Garden
San Marcos, CA