A sunk cost is money, time, or effort that has already been spent and cannot be recovered. A sunk cost expense refers to the loss of time, money, or effort, which you can't get back. If you let ...
Watkins, Michael D., and Samuel Passow. "Sunk Costs: The Plan to Dump the Brent Spar (A)." Harvard Business School Case 903-010, April 2003.