Sunk cost

A sunk cost is money already expended without ability to retrieve the funds.

A sunk cost is different from ongoing and future expenses by a business. Sunk costs should be excluded from future decision-making because the cost was incurred and cannot change regardless of future revenue and expenses.

Sunk costs are not relevant costs, which are costs not yet incurred.

Simply put, sunk costs are unrecoverable, so forget about them and make decisions based on future revenue and expenses.