Opportunity Cost

Overview

Opportunity cost is the true cost of any choice: the value of the next-best alternative you give up. Accounting cost is what you pay; opportunity cost is what you forego. The two diverge whenever resources are scarce — which is always.

Bastiat (1850) established the foundational insight: every visible benefit forecloses an invisible alternative. Buchanan (1969) formalized it: cost is subjective, prospective, decision-maker-specific — the accountant's number and the economist's number can diverge by 10x.

Composes with expected-value-and-kelly, first-principles, pareto-principle, sunk-cost-fallacy, compound-interest.

When to Use

• Allocating budget, headcount, or founder-time across competing options
• Evaluating an investment vs. holding cash (or vs. another investment)
• Considering a "free" benefit whose hidden cost is time/attention
• Any "this is good for X" claim that ignores the alternative use of the same resources
• Weighing AI capex (GPU spend, model training vs. renting APIs), an AI pivot, or a quarter of roadmap/founder-time against the best forgone alternative amid 2024–2026 AI valuations and adoption

Not when: alternatives are genuinely zero-value; resources are not scarce; decision is reversible at near-zero cost.