I might if it were really cheap, the seller had 100% feedback spread over years, I was using Paypal, there was a good return policy and the feedback said that the seller was good with returns, and if I knew a jeweller who would appraise it within the return window. Also,if my expectations were a bit low (if you want a GIA diamond, go to Bluenile).
When I was on Pricescope,several people there said they had bought from a seller called Mlopros and that they were happy with what they got. I looked at his or her site a few times and the prices seemed reasonable for what was being offered--not like you were getting a huge deal like it might seem, but that the prices were in line with the usual prices for whatever it was. There were a lot of loose diamonds on the site, but also some finished jewelry, some antiques and some other occasional pieces. The diamonds to bid on were usually terrible quality (and it was clearly written what they were, although of course the seller always said that for this quality, the diamond was better than usual) and a lot of the buy-it-now jewelrywas very low priced. But you can lookon there for yourself, if you're interested.
I never did buy anything there, I wantto repeat that.