In relative terms you don't make a lot of money unless you have somebody really marketing your site. . . . Clearly, if you're a jewelry designer who needs a specific stone, getting out-bid at the last moment is not an option. Although eBay is open to the public, there is also wholesale trading on the site, and occasionally dealers will connect with new suppliers that way. Usually anyone who has an auction has their own site. In addition to good traffic and an established name, eBay offers customers the ability to give feedback on sellers.
Positive feedback can help businesses build trust in a medium that is essentially anonymous.
The only way you can really tell is if they have a good volume and good feedback. Other than that, you can't really tell. Of course, there are disadvantages to online auction sites. We must remember that gemstones are not books or CDs and require a level of experience to purchase confidently. Trade-only networks address that problem and have the potential to offer all of the advantages of online auction sites.