Economists assign a value to the decision you did not choose it is called opportunity cost. Opportunity cost is the value of the next best alternative. It is not the value of all alternatives. Opportunity cost is also known as social cost. Opportunity cost is subjective.
Opportunity cost depends on the alternatives and varies by situation.
Sunk cost a cost that must be incurred no matter what. Choice is irrelevant. You never get the value back. We can gain benefit when we make good use of time and resources. Law of comparative advantage the individual with the lower opportunity cost of producing a particular output should specialize in producing that output.