If you select a course of action, whatever it is, you are automatically not doing something else. So if I take a job A, I’m not taking Job B, Job C or starting business X or Y. Why is opportunity cost not a sum of all the alternatives i.e. B + C + X + Y? The alternatives would probably add up to infinity. Where is the flaw in this logic?
Opportunity cost is by definition the cost of the NEXT BEST THING that you gave up.
so in this case - you would have ranked the alternatives first (by whatever criteria)
then take the cost of the next best thing you gave up.
I believe the flaw in your logic is that you can’t do ALL of those things, you can only do ANY one of those things. So your opportunity cost can only be as much as the most valuable opportunity you are forgoing.
The flaw is an “either-or fallacy”, meaning you either do A or B…But there is usually something else you can do. You can do A and B, unless something is mutually exclusive.
The assumption underlying the concept of opportunity cost is mutual exclusivity. If you can take advantage of all opportunities, there’s no opportunity cost. If you can only take advantage of one opportunity (or alternately, or some of the opportunities), you lose the option of taking the next best one(s).