Opportunity cost

Opportunity cost is the value of the next best alternative foregone whenever a decision is made. It is a foundational concept in economics and investing because every choice — even the right one — comes at the cost of the alternative not chosen.

How opportunity cost works

If a decision uses a finite resource (money, time, energy), the resource cannot simultaneously fund the alternative. The opportunity cost of choosing Option A is the benefit that would have come from Option B.

Examples

Investment example: Putting $10,000 into a savings account earning 3% means foregoing the chance to invest in shares that historically average 7%. The opportunity cost is roughly $400 per year in returns.

Career example: Studying full-time foregoes salary that could have been earned working full-time. The opportunity cost includes both the foregone wages and the compound interest they would have earned if invested.

Business example: Spending engineering hours on Feature A means Feature B is delayed. The opportunity cost is the customer value Feature B would have delivered.

Why opportunity cost matters

• Reveals the true cost of decisions — sticker prices ignore what else the resource could have done
• Drives better capital allocation — comparing alternatives on a like-for-like return basis improves portfolio outcomes
• Underpins discount-rate thinking — future cash flows are worth less than today’s because today’s money has alternative uses
• Frames “free” decisions properly — even decisions with no out-of-pocket cost have opportunity cost (e.g., volunteering time)

Practical application

When evaluating any major financial decision — buying versus renting, paying down debt versus investing, accepting a job — compare not just the option’s absolute return but the return relative to the best alternative. The discipline often changes the decision. Net worth projections that ignore opportunity cost overstate the value of suboptimal choices.