Finance term
Sunk Cost
Also known as: irretrievable cost, stranded cost
Definition
A sunk cost is money already spent and non-recoverable. Because it cannot be changed by any future decision, it should not influence go-forward choices — though the 'sunk-cost fallacy' causes many people to let it.
Detailed explanation
Sunk costs are economic history. Whether you've spent $50,000 on a marketing campaign that produced no leads, or $500,000 renovating a location that underperforms, those dollars are gone regardless of what you decide next. The rational decision is to evaluate only future costs and benefits — forward-looking cash flows — when deciding whether to continue, pivot, or exit.
The sunk-cost fallacy is the human tendency to continue investing in a losing position because of what's already been spent: 'We've put $200K into this — we can't stop now.' This logic is economically irrational. The relevant question is: does the next dollar invested generate more than a dollar of expected return, given current information? Past spending doesn't change that calculation.
For business owners, sunk-cost thinking most commonly appears in: (1) holding onto underperforming equipment rather than selling it, because of what was paid; (2) continuing a money-losing product line because of development investment; (3) staying in an expensive lease because of fit-out costs; (4) avoiding refinancing decisions because of origination fees already paid on the existing loan.
In loan restructuring and workout situations, lenders explicitly apply sunk-cost thinking. The question is not 'how much have we already lent?' but 'given the current situation, is extending more credit, restructuring, or exiting our best forward-looking option?' Forbearance and workout decisions are made on prospective expected recovery, not historical loan balance.
◈ Worked example
- Owner spent $80K renovating a poorly-located retail space. Sales are weak. Sunk-cost fallacy: 'I can't close — I spent $80K on this location.' Rational analysis: the $80K is gone either way. The decision should be based solely on future projected cash flows of continuing vs. closing costs vs. subletting.
- Business borrowed $500K for a product launch that failed. Still owes $350K. Sunk-cost trap: continuing to operate the failed product to 'pay off the loan.' Rational analysis: the $150K already repaid is a sunk cost. The decision is whether expected future revenue from the product covers remaining operating costs + debt service.
- Refinancing example: Owner paid $25K in origination fees on a current loan 18 months ago. A better loan is available but 'I don't want to lose the $25K I paid.' The $25K is a sunk cost — already spent, non-recoverable. The refinancing decision should be based entirely on the net present value of interest savings vs. new origination costs.
Common questions
The most-asked questions about Sunk Cost — answered straightforwardly.
What is the sunk-cost fallacy? +
The sunk-cost fallacy is making decisions based on past unrecoverable expenses rather than forward-looking expected value. It leads to irrational continuation of losing strategies, underperforming investments, or failed products. The rational corrective: ask only 'what are my expected future returns and costs from this point forward, independent of what I've already spent?'
How does sunk cost apply to refinancing a business loan? +
Origination fees paid on an existing loan are sunk costs — they should not prevent refinancing if the forward-looking NPV of refinancing is positive. The analysis should compare future interest savings (over the remaining loan life) against new origination fees and any prepayment penalties. Fees already paid are irrelevant to that calculation.
Are sunk costs ever relevant to a decision? +
Rarely, but there are edge cases. Sunk costs may be relevant for tax purposes — if the cost creates a tax loss, the tax benefit is a future cash flow that should be considered. They may also be relevant for accounting (impairment decisions require recognizing sunk costs as losses). But for operational go/no-go decisions, sunk costs should be excluded from the analysis.
Further reading
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