In reality, an auction resembles Observer. Every auction bidder has a number paddle that is raised whenever they want to place a bid. Whenever the paddle is raised by a bidder, the auctioneer acts as the subject by updating the price of the bid and broadcasting the new price to all bidders (subscribers).
The following figure, courtesy of www.sourcemaking.com, [j.mp/observerpat], shows how the Observer pattern relates to an auction: