the.com/sunk cost

means The resources you've already spent and can never get back, which shouldn't logically factor into decisions about what to do next — but almost always do.

from Pure economics-speak, not folklore: 'sunk cost' surfaces in 20th-century economic theory to describe costs already incurred and irretrievable, 'sunk' like a ship gone under — unrecoverable, done, settled on the seafloor. The term became shorthand for the 'sunk cost fallacy,' the very human habit of pouring in more time or money just to honor what's already lost, rather than cutting losses. The word didn't come from a story — it came from accountants needing a blunt way to say 'that money isn't coming back, stop factoring it in.'