For Auctions, remember that bidding is done in specified increments. The user with the highest successful bid "wins" the ability to purchase the item.

Note that the seller has a reserve price, and even if you are the highest bidder at the end of the auction but did not meet the reserve price, the seller reserves the right not to sell you the item!

In Dutch Auctions, the final item price is the lowest successful winning bid by the highest bidders.