Civil Engineering becomes “mud. And there is always mud.” Boxing is “hit. don’t get hit.” Economics is “incentives matter. Opportunity costs.” If you can get your mind around those two points then you’ll be doing better than all too many professional economists.
The first is obvious, people react to what they’ll get from doing or not doing something. The second is rather more subtle and it’s something that economists really do insist upon. The cost of doing something is whatever you give up to do that thing.
The cost of making love to your mistress is not making love to your wife that afternoon, not unless your lifestyle is very much more exciting than that of most of us. Being slightly more serious one of the costs of going into business making mobile phones is not being able to use the capital, the buildings, the land, to make cars.
We’ve had to give up our ambitions to be Henry Ford in order to be one of the Ambani brothers (preferably the one making money).
There are always opportunity costs because we can always be doing something else other than what we actually are doing. The cost of whatever it is is whatever it is we give up to do it.
That mistress and wife point is probably one that makes more sense to an older, rather than younger, man.