The value of the price paid is called costs

"...Action is an attempt to substitute a more satisfactory state of affairs

for a less satisfactory one. We call such a willfully induced alteration

an exchange. A less desirable condition is bartered for a

more desirable. What gratifies less is abandoned in order to attain

something that pleases more. That which is abandoned is called the

price paid for the attainment of the end sought. The value of the

price paid is called costs. Costs are equal to the value attached to the

satisfaction which one must forego in order to attain the end aimed

at." Mises, Human Action, p.97