Since the auctioneer realized he had milked us as far as he could, he let the piece go. I knew it, but I suffered the violation to get what my wife wanted. Many bidders do the same, but most never know they were cheated. He is not a real buyer. He's a straw man whose only purpose is to place bids to drive the price up on legitimate bidders.
Shills can be employees, relatives, or friends of the auctioneer, or of the seller.
Astute bidders also go to auctions fearful the auctioneer will take a bid when no one is bidding, but there's a big difference. The former fear an error that seldom happens and never causes a problem. The latter fear an intentional wrong that always costs the high bidder money. At an auction, the auctioneer looks across a sea of faces, and all the faces look back at him. Since bidders have a variety of secret signals, it's common for other bidders not to know where competing bids are coming from.