Sunk cost
Also called: Throwing good money after bad
Continuing something because of what you've already put into it, not because of what it will return.
How to spot it
Is “we've already spent so much” the reason to carry on?
Example
“We've spent three years on this, so we can't stop now.”
How to answer it
Past costs are gone either way. Ask only what the next step costs and returns.
Related
- Wishful thinking: Believing something because you want it to be true.
- Broken window fallacy: Counting what is spent and gained, and ignoring what that money would otherwise have done.