Posted By:
warshawlawThis format is not unique--Naxcom does this--the seller lists the item at an offer price and the buyer makes an offer. If the seller accepts it, the item sells.
You also see this function in the stock market, where shares can be bought/sold at market or at specified prices.
I also suspect that ebay is trying to cut into some of the offline auction-ending offers by providing a legitimate mechanism in ebay for you to offer on a card. I'd like to see this available for auctions too.