Doing nothing is expensive.
Opportunity cost is the value of the lost opportunity, the benefit of the thing you could have done instead of what you're doing now.
How much does it cost to go to Stanford Business School? Well, there's the out of pocket costs, things like tuition and housing, but there's also the cost of the job you gave up to go.
Opportunity cost is at its most expensive when we miss opportunities. It's not merely the cost of making a choice, it's the real penalty of standing by as something important is happening without us.
The opportunity cost of not looking for a new job, of not building a new plant, of not listening to a new idea—these are significant, and we overlook them all the time.
It's almost impossible to live a good life if you're measuring the opportunity cost of everything you do. FOMO (fear of missing out) is a crippling syndrome, because you're always looking over someone's shoulder to see if someone (or something) better is across the room.
But even though FOMO is a joy killer, ignoring the cost of missing out is still a problem.