noun
Economics term for a cost that has already been incurred and cannot be recovered. Often used in the phrase サンクコスト効果 (sunk cost effect) or in discussions of decision-making.
サンクコストを考慮してはいけないと経済学の授業で習った。
I learned in economics class that you shouldn't consider sunk costs.
Because of the sunk cost effect, people sometimes keep making wasteful investments.