posted by Ami .
Why must the opportunity cost of a decision always be something desirable?
opportunity cost is the value of the next best thing when making a decision.
Say you have a decision to buy A or B. You know the value of each decision. You choose A, and it cost you the opportunity to choose B.
I can't answer your question, mainly because of the word "desirable". That is not an operationally objective word, what is desirable for one is not desirable to another.