The minimum a seller has specified he will accept at auction. The bidder at an auction is merely making an offer. This is not affected by the auctioneer stating that the highest bidder will be the purchaser. The minimum offer that an auctioneer should accept is the reserve price specified in the owner's instructions.
WHERE THE RESERVE PRICE IS ANNOUNCED
A prior notice about a reserve price, or no reserve price is only part of the invitation to treat. The announcement of a reserve price by the auctioneer indicates only to the bidders that an offer below the reserve price will or will not be considered.