Possible game changer: Instead of guessing at the cross hairs of price to volume, vendors can actually hear the consumer's opinion real time (not after a month of testing). Instead of running a/b testing, they can begin to see outliers and future trends. They can learn consumer behavior by responding to back channel offers from consumers and then roll out appropriately with sales according to offers received. The nice thing is the control instead of turning over your inventory to a third party liquidation specialist that is going to make a margin on all the down channel overstock. It allows all vendors to have a certain outlet/flash possibility and increases engagement and page views. This isn't a site though, it's a button or meebo like bar that you can send data back when you're on the product page to the vendor letting them know you'll buy at $x price. The key would be the right amount of engagement and feedback from the vendor. If nothing happens after the offer is made (ie counter offers, other similar offers, something) then I think users don't engage.