The auction company is induced as a third side in standard auction model which considers only bidders and seller. The auction company takes some commission from the winner of the auction. The main result is that the volume of the commission rate k has both effects on the bidder's bid strategy and the expected profits of the seller: bidder's bid becomes more passive but its expected profits is not dependent on the commission rate k; the seller's expected profit has really decreased. In fact, the commission o...