Defininion sunk cost fallacy?
The sunk cost fallacy explains why people are sometimes very set in their ways, holding on to opinions after the premises they are based on have been debunked – even when this proves harmful.
It refers to our tendency to follow through on the path we are on, particularly once we have invested time, money or energy in it.
If it is all three, for instance when we’ve supported a disappointing political candidate or cause financially and spent months canvassing, we are more likely to keep supporting such a person. We may even ignore evidence that this politician is actually disappointing or corrupt. Rationality has very little to do with it.
Throwing good money after bad
The sunk cost fallacy is related to commitment bias, which explains why we tend to remain committed to our past behavior, particularly when it was exhibited publicly. Commitment bias is more about losing face though, while the sunk costs is more about refusal to accept a loss.
The two of them together can do a lot of harm, because decisions made on the basis of sunk cost argumentation with a commitment bias can be against your own interest.
See also Commitment bias.