Economics has never been my strong point. (see my bank account for proof)
- breaking a window for no reason costs money, so it's economically bad
- but actually it generates labour and might be economically good?
- no, that's a fallacy, you've made the room unusable and reduced its economic worth + wasted labour on a useless repair task instead of improving the system.
The rest of the article says that it might not be a fallacy if you break a significant part of the system and not just a window.
Disclaimer: I don't fully understand the rest of the propositions in the article.
The idea is that the real cost of any choice is the value of the other choices you could have made. That is, if you have 100$ and can buy either a farm or a factory with them, the cost of the farm is not 100$, it is the wealth that you could have gained if you had bought the factory instead (over some time horizon). Of course, in many real-world situations this is not a computable value, as the alternatives are far too open-ended, but still it's a useful way to model certain problems.
Microeconomics and macroeconomics aren't the same thing. Just because markets are going up doesn't mean you actually own enough resources to benefit from it.