Fungibility mindset and its counterpoints

Any good or service (henceforth "thing") that you want enough to get, you either make on your own or buy. Generally, you buy a good or service with money, at the market's price P. Suppose you earn money at a rate W, in dollars per unit of effort, and you'd make the thing you want with K units of effort. If P/K > W, you should make that thing beyond your own use, and so earn more money than your current method. If P/K < W, then you should work for money as you do, and buy the thing, having expended effort P/W < K.

That argument abstracts over all goods and services. So you should buy everything you want, except the thing with greatest-for-you P/K. Expend all your effort towards getting what you want by making that easily-made thing. We may call this fungibility mindset.

Few people really follow fungibility mindset. Partly, this is sith people are irrational. There are also real limitations of fungibility mindset in most people's lives.

Selling a thing often takes extra effort S, beyond that effort K to make the thing, for a few common reasons:

• You might get money for a thing directly. In that case, you must find customers, or present your work so the customers will find you.
• You might get money for a thing as an employee. In that case, you must find employers, make yourself appealing to them, and repeat the process to make up for hiring rates.
• You would use the thing yourself at lower quality, reliability, or convenience than the existing market accepts (e.g. cooked food). Selling it requires extra effort to improve it.
• The thing you want and can make may be a "service" you can only do yourself (e.g. sleeping, eating, learning, exercising). The way around that would be a radical technology to let one outsource those "services", thus making S the effort to devise or obtain such technology.

Suppose you make gizmos to earn W, and can make widgets for effort K, and can sell them with extra effort S, or buy them for P. Naively, you should switch to making widgets, to earn money, if P/K > W. The overhead implies that you should switch only if P/(K + S) > W, in which case P/W > K + S. You should buy widgets, instead of making them for your own use, iff P/W < K. Given positive S, there are some types of widgets for which neither making them to earn money nor buying them is advisable, i.e. K + S > P/W > K. In those cases, it makes sense to make things besides your specialty for yourself, and reluct to use money.