Hmm, not sure if we understand each other. To clarify, in Brazil we have "used auto fairs", a day-long event where a company provides a place where individuals can take their cars to sell. Individuals can go there and buy directly from the sellers (dealers can go there and buy too, but that sort of defeats the point for the sellers).

I tried googling the term in English and didn't get many hits, so I assume you call it by another name. And if for some odd reason you don't have such events in N. America, you should start a business and get rich easily :-).

Another interpretation is that you do have access to auto fairs but would still prefer to shop on the net, while still having the option to go through a third party. But I guess that scenario is not so attractive to the third party (unless that third party is a dealer which again defeats the point).