The idea
A sunk cost cannot be recovered by the current choice. Decisions should compare future consequences of available options. Past spending matters for accountability and learning, but spending more does not recover an amount that is already irretrievable.
Worked example
A theater paid 900 units for an unusable backdrop. Repair would now cost 500; renting a suitable replacement would cost 250. Both would support the same performance quality. Choosing repair because the theater already spent 900 confuses the budget history with the next decision. Under the stated assumptions, renting costs 250 less from this point onward. The board separately investigates why the original purchase failed and improves its procurement process.
Use it carefully
Some apparently past investments create future benefits, such as compatible equipment, transferable skills, or resale value. Those consequences belong in the comparison. The sunk-cost principle does not mean ignoring contracts, cancellation charges, relationships, or safety. It means identifying which costs truly differ between options now. Preserve the history for evaluation without allowing embarrassment to control the next allocation.
FROM UNDERSTANDING TO ACTION
Put it to work.
Revisit an unfinished commitment. Separate irreversible past costs from future switching costs before deciding whether to continue.
RETRIEVE. REASON. REMEMBER.
Knowledge check.
Choose one answer for each question, then check your reasoning.
Sources & further reading.
Links support the core concepts or identify the book. Examples, exercises, and critical analysis are original Institute material. Source checks are not an independent expert review of every claim.
- OpenStax: fixed, variable, and sunk cost distinctions ↗
OpenStax: fixed, variable, and sunk cost distinctions; supports the core concept. Scenarios, calculations, and practice questions are original. Source reviewed 2026-10-19.