Sunk Cost Fallacy

The sunk cost fallacy is a cognitive bias that challenges our decision-making. Humans irrationally value what they’ve already invested, whether money, time, or effort, even when those investments can’t be recovered.

In software development, teams often continue working on a feature or product without making progress simply because “we have come this far.”

Understanding this fallacy allows engineers and managers to make more rational choices: past costs should be ignored when deciding the future. Instead, consider current facts and future benefits.

If a rewrite or switch to a third-party solution will clearly save time and money from this point forward, do that, regardless of how much was sunk into the old approach.

Overcoming sunk-cost bias is tough because it requires admitting past efforts were in vain, but in technology it’s crucial to learn to let go when evidence demands.

• Don't stay stuck based on past investments. The fact that 'we've invested a year already' is not an excuse to continue if it's clearly not working.
• Healthy engineering organizations pivot or stop projects that no longer make sense. Continuing a bad project just because of sunk costs usually leads to greater loss.
• Use clear measures and decision points: 'If we don't meet target X by end of quarter, we'll re-evaluate or discontinue.'
• Teams should feel safe admitting a project isn't working without fear of blame.