Sunk cost fallacy
Etymology
A "sunk" cost is money or effort already spent and unrecoverable — sunk in the sense of gone under, beyond retrieval. The rational rule is that such costs shouldn’t affect future choices; the fallacy is that they stubbornly do.
noun · /sunk kost FAL-uh-see/
Sticking with something because of what you’ve already spent, rather than what it’s worth from here.
What it names
The pull of "I’ve come this far" — the finished movie you keep watching, the degree you don’t need, the project no one believes in anymore.
Example
We kept pouring money into the failing rollout out of pure sunk cost fallacy — no one wanted the earlier spending to be "wasted."
Related idea
Loss aversion feeds it: abandoning the investment feels like accepting a loss.