How do real auctions stop shill bidders?

There’s a lot of concern on eBay about shill bidding, where a confederate of the seller bids on an item to get a higher price.

How do real, physical auctions run by an auctioneer prevent this kind of thing?

In ebay you may back out but in real life you may get stuck with the item.

In my experience, shills are fairly common at auctions. It depends on how honest the auctioneer is. What really makes me mad is when an auctioneer openly bids on an item himself. That never used to happen, but is becoming common.

After going to many farm auctions over the years, I’ve finaly decided that auctions are rarely a good way to buy anything. Assuming there is a large crowd at an auction that knows the market price for items, actually buying something seems to imply that you have paid more than any other interested and informed buyer is willing to pay. That, on top of the fact that shills are fairly common, keeps me away from auctions anymore.

If the auction place sees that a buyer & seller of an item have the same account, then they know someone is bidding on their own stuff.