Sunk cost fallacy — definition

What is sunk cost fallacy?

Sunk cost fallacy is a cognitive bias where you continue an activity just because you've already invested time, money, or effort into it — even when rational analysis tells you to stop.

Sunk costs are expenses that have already been incurred and cannot be recovered. They shouldn't influence future decisions — but in practice, they do, and strongly.

Quick Answer

The sunk cost fallacy is a cognitive bias where you continue an activity just because you have already invested time, money, or effort — even when rational analysis says to stop. Because sunk costs cannot be recovered, decisions should focus only on expected future outcomes. It is driven by loss aversion (a loss hurts about twice as much as an equal gain feels good), a sense of waste, ego, and hope. In investing it shows up as holding falling stocks or averaging down to avoid realising a loss; a useful test is the "fresh start" question.

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Examples from everyday life

• You watch a bad movie to the end because "you already paid for the ticket"
• You eat too much at a restaurant because "it's a waste to leave it since I paid"
• You finish studies in a field you don't like because "you already spent 3 years on it"

Sunk cost fallacy in investing

Holding falling stocks

The most common trap: you bought stocks for 100 PLN, they dropped to 50 PLN. Instead of selling and moving capital to a better investment, you hold — because "you don't want to realize the loss". The question isn't "how much did I lose", but "do these stocks have a chance to rise?".

Averaging down

You buy more of falling stocks to "lower the average purchase price". Sometimes this makes sense (good company in temporary trouble), but often it's deepening losses in a bad investment.

Subscriptions and fixed costs

You pay for a gym you don't use. For an online course you don't finish. For insurance you don't need. "It's a waste to quit since I already paid" — but continuing to pay is another loss.

Real estate

You poured 200,000 PLN into renovating a rental apartment, but the location doesn't attract tenants. Instead of selling at a loss and freeing up capital, you wait "for it to pay off" — and lose more.

Why do we fall into this trap?

• Loss aversion — psychologically, a loss hurts 2x more than a gain of the same size feels good
• Sense of waste — the brain doesn't want to admit that money was "wasted"
• Ego — admitting a mistake is difficult
• Hope — "maybe it will turn around"

How to avoid sunk cost fallacy?

1. Ask: what would I do if I were starting from scratch? — If you didn't have these stocks, would you buy them today at this price?
2. Set stop-loss upfront — before you invest, determine the loss level at which you sell
3. Focus on the future — what matters is what's ahead of you, not what's behind
4. Regular portfolio review — once a quarter, evaluate each position anew
5. Accept losses — it's a normal part of investing

How Freenance can help

Freenance shows the results of each investment separately — you see which positions are losing and for how long. This helps make rational decisions about selling instead of emotional holding. Regular portfolio reviews in Freenance are your protection against sunk costs.

👉 Manage your portfolio rationally with Freenance — freenance.io

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FAQ

What exactly is the sunk cost fallacy?

The sunk cost fallacy is the tendency to keep investing time, money, or effort into something just because resources have already been committed, even when continuing no longer makes rational sense. Sunk costs cannot be recovered, so a rational decision should focus only on expected future outcomes.

Why does money already spent feel so hard to ignore?

Human decision making is shaped by loss aversion — psychologically, an admitted loss hurts more than an equivalent gain feels good. Combined with the desire to avoid feeling wasteful and ego protection, this makes it emotionally difficult to walk away from an unsuccessful investment even when the data says you should.

How does sunk cost fallacy show up in investing?

Common examples include holding a losing stock just to avoid realising a loss, doubling down on a falling position without a sound thesis, or staying in an expensive fund only because of past entry fees. The trap is letting the entry price drive the decision, instead of the asset's current outlook.

How can I tell if I am stuck in a sunk cost trap?

A useful test is the "fresh start" question: if you had cash today instead of this position, would you buy it at its current price? If the honest answer is no, you are likely holding it only because of money already spent rather than for its forward-looking merits.

How can I avoid making decisions based on sunk costs?

Set objective exit criteria before entering a position, review your portfolio on a regular schedule, and evaluate each holding on its current fundamentals and outlook. Accepting that losses are a normal part of investing makes it easier to redeploy capital into better opportunities rather than anchoring on past costs.