I have written several times before about Peerflix -- Now that I've started applying some tags as well as categories to my items you can now see all the Peerflix stories using that link -- and the issues behind doing a P2P media trading/loaning system. Unlike my own ideas in this area, Peerflix took a selling approach. You sold and bought DVDs, initially for their own internal currency. It was 3 "Peerbux" for new releases, 2 for older ones, and 1 for bargain bin disks.
That system, however, was failing. You would often be stuck for months or more with an unpopular disk. Getting box sets was difficult. So in December they moved to pricing videos in real dollars. I found that interesting because it makes them, in a way, much closer to a specialty eBay. There are still a lot of differences from eBay -- only unboxed disks are traded, they provide insurance for broken disks and most importantly, they set the price on disks.
One can trade DVDs on eBay fairy efficiently but it requires a lot of brain effort because you must put time into figuring good bid and ask prices for items of inconsequential price. Peerflix agreed that this is probably a poor idea, so they decided to set the prices. I don't know how they set their initial prices, but it may have been by looking at eBay data or similar information.