Cognitive bias
Sunk Cost Fallacy
Keep going with something because of what you've already invested, not because it's still worth it.
Keep going with something because of what you've already invested, not because it's still worth it.
Example
"We've already spent £40,000 on this software, we can't stop now," even though finishing costs another £60,000 for something nobody actually wants.
Money, time, or effort already spent is gone regardless of what happens next. The sunk cost fallacy weighs that past spending as if it were still a reason to keep going, rather than looking only at the cost and benefit of continuing from today.
A rational decision only cares about future costs and future benefits. The £40,000 already spent doesn’t change whether the remaining £60,000 is worth spending.
Ask: “if I hadn’t spent anything yet, would I start this today?” If the answer is no, the past spending isn’t a reason to continue.