Abstract: Group-buying auction is a new kind of dynamic pricing mechanisms on the Internet This mechanism makes the bidders as a group through Internet to get the volume discounts As a variant of double auction,what condition Group-buying suits is not clear and is valuable to study This paper analyzed the seller’s profit for the group-buying auction when the economies of scale are considered,and proved that the group-buying auction will overmatch the fixed-pricing mechanism if the seller can always satisfy the bidders’ demand,which provides the Group-buying auction a suitable point.

Key words: dynamic pricing mechanism, group-buying, online auction, fixed-pricing mechaism