Every hour and every dollar spent on one thing is unavailable for another. The opportunity cost of a choice is the value of the best alternative you gave up to make it — the hidden price tag on every decision (see section “Opportunity Cost: The Hidden Price Tag of Every Decision” for the full treatment). The calculus turns sharp at career forks. Take the classic one: a salaried job buys stability, health insurance, and employer retirement contributions; building a business buys autonomy and uncapped upside, set against the odds — the Small Business Administration reports that about 20% of new firms fail within the first year and roughly half within five. Neither path is free; each is paid for in the other. The discipline is to price the alternative you are not choosing — in time as much as in money — before you commit.