In microeconomic theory, the opportunity cost of a choice is the value of the best alternative forgone where, given limited resources, a choice needs to be made between several mutually exclusive alternatives. Assuming the best choice is made, it is the "cost" incurred by not enjoying the benefit that would have been had by taking the second best available choice. The New Oxford American Dictionary defines it as "the loss of potential gain from other alternatives when one alternative is chosen". As a representation of the relationship between scarcity and choice, the objective of opportunity cost is to ensure efficient use of scarce resources. It incorporates all associated costs of a decision, both explicit and implicit. Thus, opportunity costs are not restricted to monetary or financial costs: the real cost of output forgone, lost time, pleasure, or any other benefit that provides utility should also be considered an opportunity cost.

In economics, economic value is a measure of the benefit provided by a good or service to an economic agent, and value for money represents an assessment of whether financial or other resources are being used effectively in order to secure such benefit. Economic value is generally measured through units of currency, and the interpretation is therefore "what is the maximum amount of money a person is willing and able to pay for a good or service?” Value for money is often expressed in comparative terms, such as "better", or "best value for money", but may also be expressed in absolute terms, such as where a deal does, or does not, offer value for money.