Opportunity Cost
The real cost of any choice is the next-best alternative you give up.
Author
Classical economics (Friedrich von Wieser; mainstream microeconomics)
Model type
About
Opportunity cost reframes decisions from “What does this option cost?” to “What am I giving up by choosing it?”. Because time, capital and attention are scarce, selecting one path excludes others. Sound choices compare options on a common basis (value, utility, ROI, joy) and focus on marginal differences, not averages or sunk costs.
How it works
Counterfactual – define the best thing you would do if you didn’t choose this option; that’s the benchmark.
Marginal, not total – compare Δbenefit − Δcost between options; ignore sunk costs.
Constrained resources – time, cash, capacity and optionality are scarce; choosing A consumes some or all of them.
Hidden costs – fatigue, complexity, lock-in and foregone learning are often the largest opportunity costs.
Relative advantage – even if you’re good at two things, do the one with the lower opportunity cost for you (ties to comparative advantage).
Use-cases
Capital allocation – project A vs buybacks vs debt paydown vs acquisition.
Product roadmap – what you don’t build this quarter.
Hiring & time – meetings, context switches, side projects; value of deep work.
Pricing & discounts – short-term volume vs long-term willingness to pay.
Career choices – role, location, equity vs cash, learning paths.
Operations – using scarce machines/teams on low-ROI work blocks higher-value jobs.
Step-by-step
List real alternatives – include “do nothing” and the best use of time/capital you could choose instead.
Set a single yardstick – e.g., £NPV, contribution per hour, learning/option value; convert each option to that unit.
Compare at the margin – compute incremental benefit and cost vs the best alternative, not vs zero.
Price the intangibles – put rough £ or score ranges on risk, focus, speed, and option value.
Pick the winner & schedule the rest – choose the highest net value now; park others with review dates.
Revisit on new information – if the counterfactual improves (or constraints change), re-run the choice.
Pitfalls & Cautions
Sunk-cost fallacy – past spend/time is gone; decide on future incremental value.
Phantom alternatives – comparing against an option you wouldn’t actually execute.
Wrong unit – mixing cash, impact and vanity metrics; force a common yardstick.
Time blindness – ignoring delay costs; sometimes “good now” beats “great later”.
Lock-in – choices that kill future options can have a large opportunity cost; price optionality.
Over-optimising pennies – spending hours to save small costs while giving up high-value work.
Related Mental Models
Click below to learn other mental models
Probabilistic Thinking
Reason in degrees of belief, not certainties: use base rates, ranges, and expected value—then update as evidence arrives.
Regret Minimalisation Framework
Project yourself to the decision horizon and choose the option that you will regret least. Weight omissions heavily, and treat reversibility as a key lever.
Second Order Thinking
Consider the long-term and indirect consequences of decisions, rather than just the immediate or obvious ones.