Opportunity cost
Estimating the value of resource use for a specific activity in term of the opportunity cost is a standard concept in economics but it seldom applied in practice because of the difficulty of establishing an acceptable measure. It is possible to ascertain the difference in value between the uses of resources without any constraints as opposed to their use with them, because of environmental objective. For example, the obligations placed on the ownership of an historic building by being listed, and its subsequent maintenance, are likely to reduce the market value or rents derived from it (Allinson et al. 1996). The difference can be taken as an indication of its heritage value. The problem is that this is almost certainly and under-valuation as it regards conservation in purely market terms because non-use benefits and externalities are ignored, such as the benefits accruing to tourists wishing to look at conserved building. A possible resolution of this omission is referred to in discussing replacement cost.