The winner’s curse
When bidders estimate the same uncertain value, the highest bid can come from the largest overestimate. Failing to account for that can leave the winner paying more than the item is worth. This is the winner’s curse.
A sealed jar of money is a simple example. Everyone is bidding for the same amount of cash, but nobody can count it before the auction.
In this example, each bidder offers their estimate.
The winner pays $100 and receives $80, losing $20.
Why the highest estimate needs caution
These three estimates average $80, exactly the amount in the jar. But the auction selects the highest estimate, not an average one. The bidder who overestimates most is also the most likely to win.
That is why accurate estimates on average do not guarantee profitable purchases. The auctions you win can be the ones where you were unusually optimistic. The winner’s curse describes this selection effect; it does not mean every auction winner loses money.
Bidding with an uncertain value
The same problem appears when companies bid for mineral rights or buyers estimate an item’s resale price. Before bidding, consider what it would mean if every other buyer valued it less than you did.
A cautious offer accounts for that possibility. The appropriate adjustment depends on the uncertainty and on what the other bidders know. There is no discount that works for every sale.
Personal value and common value
A concert ticket can be worth more to one person because they enjoy the band more. That difference is a preference, not an estimation error. The cash in the jar is worth the same amount to whoever buys it. Economists call that a common value.
Many purchases combine both. You may want a painting for your wall and also care about its eventual resale price.