What is Option Value?

Legal Definition
In cost–benefit analysis and social welfare economics, the term option value refers to the value that is placed on private willingness to pay for maintaining or preserving a public asset or service even if there is little or no likelihood of the individual actually ever using it. The concept is most commonly used in public policy assessment to justify continuing investment in parks, wildlife refuges and land conservation, as well as rail transportation facilities and services. It is also recognized as an element of the total economic value of environmental resources.

This concept of “option value” in cost–benefit analysis is different from the concept used in finance, where the term refers to the valuation of a financial instrument that provides for a future purchase of an asset. (See Option time value.) However, the two can be related insofar as both can be interpreted as a valuation of risk factors.
-- Wikipedia