Well, that's why basically nobody builds them in places like New York or SF. Even so, I think you're underestimating how long it takes to make it to a net profit as a startup. Even in one of these cities, the planning-to-profit timeline is under 5 years.

Even 432 Park Avenue, the new huge luxury tower in NYC, took 3 years. A random startup takes a lot longer to get to the money.