[jarrodtaylor]

I'm only not paying the cost of living if you isolate the suburbs from the city.

Example:

In Atlanta (my home town) there are about half a million people living in the city. Though there are poor areas, the economy as a whole is much bigger than that, but the infrastructure isn't - even if you removed the cars. Here's where it gets tricky. Add in the population of the surrounding suburbs and the number jumps from half a million of over 6 million. If all of us lived in the city, not only would it be even more overcrowded, but it would collapse. If we somehow managed to make it work, it would cease to be small connected communities and become one giant urban sprawl. Look at NYC or LA for example. Riding a bike from one end to the other doesn't work so well.

At the same time, if you removed the city from the suburbs they would go broke. Suburbs without cities are just small towns, which don't usually have bustling economies and are often poor (relative to a city).

Suburbs are the natural growth/overflow of cities. When a city gets too big to sustain itself it either spreads the population out with suburbs or becomes an overpopulated, overcrowded urban area that's big enough to need to drive everywhere anyway (or take a cab). All those people have to go somewhere.

If my cost of living went up 10x, I couldn't afford to live this way. If it happened to everyone in the suburbs here and we all had to live in the city, the city would fall apart.

Instead of the historically traditional city with surrounding small towns, we connected the towns to each other and to the city with cars. It's one big culture, and one big economy.

What I think will be the most interesting, long term, is what will happen when the need to commute starts to drop. Remote working already has a lot of growing traction in the tech industry, but I can see it spreading to lots of other industries as well. Most jobs that aren't transportation or retail can be done, at least most of the time, from a home office. A 20% increase in remote working would have a huge impact on how everything fits together.

[adrianN]

"overcrowded urban area that's big enough to need to drive everywhere anyway (or take a cab). All those people have to go somewhere."

I don't think that conclusion is true. First of all there doesn't have to be a reason to drive to the other side of the city, if urban planning was done properly and everything you need for your daily life is within walking distance. Secondly, high population density makes public transport highly efficient, so instead of taking a taxi, you can take a train or a bus.

[jarrodtaylor]

Most of our cities (maybe all?) haven't been planned that way though. They usually start out as a small town, then they get a large influx of people and businesses who all want different things, and the city ends up growing by leaps and bounds with very little planning. Then it happens again and again, in waves of growth. Even if the expansion was somehow planned well, the existing part of the city won't be prepared.

Also, there are plenty of reasons to travel around town that don't involve what you need in your daily life. What about when your friends want to meet at a bar on the other side of town? If that's 5 blocks, no big deal. If that's 15 miles it becomes a problem.

High population density doesn't make public transportation efficient, good planning does. If the public transportation system is designed for a city of 2 million, and the city grows to 7 million, the public transportation system won't be effifcient, or pleasant to use, at all. The unpleasantness and eneffieciency is one of the reasons so many people have cars to begin with. Private transportation takes you where you want to go, when you want to go there, in an environment of your choosing. As is mentioned in other comments here, walking when the weather is bad (cold north, too humid south) is very unpleasant no matter what.

[jarek]

"As is mentioned in other comments here, walking when the weather is bad (cold north, too humid south) is very unpleasant no matter what."

Sure, but the alternatives can be more unpleasant still. Last winter I had a walking commute of 12 minutes in Toronto. You'd have a difficult time finding someone who found a 45-60 minute drive through congested and frankly miserable GTA winter roads less unpleasant.

[asynchronous13]

"Add in the population of the surrounding suburbs and the number jumps from half a million of over 6 million. If all of us lived in the city, not only would it be even more overcrowded, but it would collapse."

Not at all! If everyone in metro Atlanta moved into the city proper, the population density would still be less than that of Paris, France.

Paris Population: 2.2 million, Paris Land Area: 40 sq mi, Paris Density: 55,000 per sq mi,

Atlanta Metro Population: 6 million [wikipedia says 5.3 mil], Atlanta City Land Area: 130 sq mi, Hypothetical Density: 43,000 per sq mi, (Actual Density: 720 per sq mi)

[rayiner]

As they say, you can fit the whole population of the world onto Manhattan. That is, of course, besides the point.

Atlanta is completely unequiped to handle that population (infrastructure-wise). It's not even clear that building out that infrastructure at that density would be wise. It's costly to build infrastructure for a city as dense as NYC. The cost of the subway system dwarfs the cost of running water and sewage piping to suburb. It makes economic sense in NYC, because space is at a huge premium. That doesn't necessarily make sense for Atlanta, a city with no natural boundaries and surrounded by cheap land.