Opportunity cost is not a real cost. No money leaves your bank account. It is a decision making tool, and treating it as an actual financial cost is a misuse of the idea.

It’s literally the price of lost opportunities. It’s not understood to be a financial cost. It’s exactly what it says on the tin. Lost opportunities may not be a financial cost, but they’re certainly a cost.

Opportunity cost isn't just a real cost. It's THE real cost.