Sunk-cost fallacy: continuing something because of what you have already spent on it, even though that money is gone whatever you decide next.

Key takeaways

  • Bids you have already placed are spent, win or lose. They should not decide whether you place the next one.
  • Penny auctions make this trap stronger: every bid adds to what you feel you have "invested," and the clock keeps offering one more chance.
  • A large study of penny auctions found that bidders became more likely to keep going the more they had already spent.
  • The best protection is a limit set before you start, and one simple question: "Starting from now, is the next bid worth it?"

You have placed 150 bids. The clock keeps resetting, and you are still in the lead every few seconds. Walking away now feels like throwing those bids away. That feeling has a name, and it is one of the main reasons penny auctions cost more than people plan.

What a sunk cost is

A sunk cost is money already spent that you cannot get back. In a penny auction, every bid you have placed is a sunk cost: it is gone whether you win, lose or stop now.

The sunk-cost fallacy is letting that money push you to keep going. The only question that matters is what lies ahead: how much more you might spend, and what you might get for it.

Why penny auctions make it worse

  1. Every bid adds to the pile. Each bid feels like an investment, so the pile you would "lose" by stopping grows with every click.
  2. The clock always offers one more chance. Because each bid resets the timer, there is never a natural moment to stop.
  3. You are often the leader. Leading for a few seconds at a time makes winning feel close, even when others are just as determined.
  4. The price stays low. A final price of a few dollars makes each extra bid feel small, while your bid spending keeps climbing.
  5. Automatic bidding hides the count. Auto-bidders place bids for you, so it is easy to lose track of how many you have used.

A worked example

You have placed 150 bids at $0.10 each, so you have spent $15. The item sells elsewhere for $60.

  • The sunk-cost way of thinking: "I've already put in $15. If I stop now, I lose it all. A few more bids and it's mine."
  • The forward-looking way: "The $15 is gone either way. If I keep going, I might spend another $10, $20 or more, with no guarantee of winning. Would I start this auction now, from zero, for that?"

If the answer to the second question is no, the $15 is not a reason to continue.

Diagram of two ways to decide after 150 bids and $15 spent. The trap: thinking you cannot stop because of the $15 leads to another bid, more spending and an even harder stop, in a repeating loop. Looking forward: accept the $15 is gone, ask whether the next bid is worth it from now, then bid only if yes and within your limit, otherwise stop.
The trap loops back on what you have spent. A good decision looks only at what comes next.

What research found

A study of more than 160,000 penny auctions found that the more a bidder had already spent in an auction, the more likely they were to keep bidding. The effect was smaller among experienced bidders, but the overall pattern helped explain why total bid spending often far exceeded the value of the items. (Source: Augenblick, "The Sunk-Cost Fallacy in Penny Auctions," Review of Economic Studies, 2016.)

  • Escalation of commitment: raising your stake to justify earlier decisions, especially after a long battle with another bidder.
  • Loss chasing: joining another auction to win back what you lost in the last one.
  • The near-win feeling: being the leader seconds before the end makes you feel you almost won, which makes the next bid feel more worthwhile than it is.

How to protect yourself

Checklist

  • Set a bid limit before you start, in number of bids or dollars, and stop when you reach it.
  • Ask the fresh-start question: "If I were joining this auction now, would I pay what it may still take?"
  • Track your total. Count your bids, not the price on the screen.
  • Set an auto-bidder limit you can afford to lose, or avoid auto-bidding altogether.
  • Don't chase losses. Treat each auction as separate, and take a break after a loss.
  • Compare with buying outright. Check what the item costs at an ordinary store before continuing.

Summary

The bids you have already placed are gone. Good decisions in a penny auction look only forward: what more you might spend, and what you might get. A limit set in advance, before the excitement starts, is the simplest way to avoid the sunk-cost trap.