Sunk Cost Fallacy

What it means

The sunk cost fallacy is the tendency to continue investing time, money, or effort into something because of what you’ve already invested, rather than based on future returns. The past investment - the sunk cost - is gone regardless of what you do next. Rationally, it shouldn’t factor into your decision at all. But it almost always does.

The pull is powerful because walking away feels like waste. If you leave a terrible film after an hour, that’s an hour lost. But staying for another hour doesn’t get the first hour back - it just loses you a second one. The sunk cost creates an emotional gravity that keeps you locked in, even when the rational move is to cut your losses.

This isn’t just about money. We do it with relationships, careers, projects, arguments, and beliefs. The more we’ve invested in something, the harder it becomes to admit it isn’t working - because that admission carries the weight of everything we’ve already put in.

In the real world

The Concorde supersonic jet is the classic case - so much so that economists sometimes call this the “Concorde fallacy.” The British and French governments continued funding the project long after it became clear it would never be commercially viable. The reasoning was always about the money already spent, never about the money still to come. Billions poured in because billions had already been poured in.

In everyday life, it’s the gym membership you keep paying for because you paid the joining fee. The degree you finish even though you realised in year two it’s the wrong subject. The relationship you stay in because you’ve already given it five years - as if those five years would somehow be restored by giving it five more.

In the workplace, it’s the project everyone knows is failing but nobody will cancel because “we’ve come this far.” The further in you are, the harder it becomes to stop - which means the worst projects, the ones that should have been killed earliest, often run the longest.