Logical Fallacies

Sunk Cost Fallacy

Continuing a failing project because of resources already invested.

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What & why

What it is
A logical fallacy in which past, unrecoverable investments of time, money, or effort are treated as a reason to keep pursuing a course of action, even when its expected future costs outweigh its likely benefits. The error is letting irreversible past spending sway a forward-looking choice that should rest only on remaining costs and benefits. Sound decisions ignore sunk costs and weigh what continuing or stopping will produce from here on.
Why it works

It works because people feel losses more sharply than equivalent gains, so abandoning a project means facing the past spend as a painful, definite loss. Continuing lets you avoid admitting the investment was wasted and protects your sense of being consistent and competent. Public commitments raise the stakes by adding the fear of looking foolish in front of others. The mind treats irrecoverable costs as if they still count, which makes throwing good resources after bad feel like loyalty rather than error.

Before & after

Before

“We've invested two years in this platform, so we must continue despite better alternatives emerging.”

After

“The two years invested taught us valuable lessons. Based on current data, pivoting now will save resources and achieve better outcomes.”

When you’ll use it

Project management: 'We've already spent $2M, we can't stop now' despite clear failure indicators

Feature development: 'We've worked on this for 6 months' when user research shows no demand

Strategic initiatives: 'We've committed to this publicly' when market conditions have changed

Pro tip

Ask: 'If we were starting fresh today, would we choose this path?' Ignore past costs.

Questions & answers

What is sunk cost fallacy in business decision-making?

Sunk cost fallacy continues investing in failing projects because of previous investments rather than evaluating future prospects objectively. It focuses on irrecoverable past costs instead of potential future returns.

How can I avoid sunk cost fallacy in business presentations?

Focus on future potential rather than past investments, evaluate projects based on going-forward economics, acknowledge when to cut losses, separate emotional attachment from financial analysis, and use objective criteria for continuation decisions.

How do I help others recognize sunk cost fallacy?

Reframe discussions around future potential, provide objective analysis tools, ask 'If we were starting fresh today, would we begin this project?', and help separate past investments from future opportunities.

Learn more

The feeling of throwing good money after bad: affective reaction in the sunk-cost fallacy (PLoS One, 2019, PMC)
The Decision Lab - The Sunk Cost Fallacy
Wikipedia - Sunk cost

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