For and on sale are often used interchangeably, and incorrectly, in my opinion. If something is for sale , a person can buy it. If it is on sale, it is offered at a reduced price.
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Anonymousdoes sale means auctionNo. "up for auction" implies a formal bidding procedure. The cookies are not up for auction; they have a fixed price; you are not bidding on them for the price you would like to pay. The cookies are just being offered for sale, that is, for the price stated.