> The megacity of >10M people is the basic functional economic unit in 2025, the minimum healthy employment market, the level at which we can provide a reasonable opportunity for productive jobs in a specialized role and a reasonable opportunity to hire someone in a specialized role

Sorry, that's nonsense. Smaller cities like Nuremberg, Ingolstadt, Augsburg etc. are perfectly viable on their own. And frankly, I can't imagine that the numbers are that much different in America.

The key thing is, the rents and housing costs in general in hyper-urban areas need to be paid for by the inhabitants, which means that their labor costs have a certain floor (ignoring assistance programs). That in turn makes hyper-urban areas less competitive in a global market. You can't really compete with Romania for developers when German developers cost twice as much or more than Romanian developers (which are equally capable), and a lot of that price difference goes to the greedy German landlord caste.