The economics simply do not work to make this sustainable. Let's not forget how expensive basic infrastructure is just because it's normalized. Water/power/sewer/trash/roads/lighting is a massive expense that just keeps getting more expensive, not to mention that you have to factor in maintenance costs.
They actually don't. Go on, try to find anything in my words that is factually incorrect.
I'll wait.
A simple verifiable fact of life: density increases do not result in cheaper housing prices. Scholarly literature is unambiguous on that point. The best positive result for new construction was a one-time 5-9% decrease in _rents_ immediately near the new construction.
Experts, who made their career in pushing urbanism, try to dance around that point.
I don't care if maintaining large roads and power and water is expensive. I'm happy to pay for the increased quality of life.
I don't see how this is unsustainable at all. It might need higher taxes or some other way of ensuring that ongoing maintenance actually gets paid for. So what?
One mile of Manhattan subway now costs more than 1000 miles of new 6-lane freeway.