Technology

They could live more modest lives in more rural areas

Living in a rural area for many people is literal hell, on top of having an array of less obvious costs. The big one is going from not needing a car to needing one. Your rent might drop $500 but you need to spend a lot on gas, insurance, maintenance, etc.

Also the social options might fall off a cliff. Humans are social creatures. I live in a city and I can walk to dozens of social activities, many of them free. Board game meetups, free music in the park, free museums with tours, free sport leagues, etc. Out in the countryside there just aren't as many options.

If you're queer or another minority, you might also have a worse time in the countryside. Maybe even fatally. A city is going to have a queer scene.

Also, there are likely more jobs in the city. Remote work and economic upheaval have changed things, but even so, most of those offices in Manhattan are full of jobs. There's just more stuff where there's more people.

Now, to your point, some people are certainly living in a $5900/mo apartment with a doorman and in-building gym that they can't afford. They could move to a less "nice" place in south Brooklyn or Queens for less than half that, likely at the cost of a longer commute, and losing easy access to a neighborhood they feel a part of. There is a housing crisis though, and people are getting priced further away. That's probably not going to be solved any time soon because capitalism doesn't care and will happily eat itself.

Anyway. Long tangent but I'm extremely pro city so I spoke up.