The intrinsic cost of urban living is much less than the intrinsic cost living in car focused suburbs. It is only more expensive now because of an under supply of urban areas caused by decades of subsidization of car focused suburbs. The ROI of spending on urban infrastructure is much higher than spending on car focused suburban development.
What? The rent in cities is vastly depressed by all the demand that the suburbs soak up. Limit the effective radius of the city to walking distance and it will skyrocket as the same number of people clamor to fit into less space.
Who is talking about getting rid of suburbs or limiting things to walking distance? That would be crazy.
There were suburbs before cars existed and there can be suburbs that don't require cars for every single trip. Before the widespread adoption of cars, suburbs were often served by streetcars that let people travel into the city. They also were walkable for trips within the suburb. Unlike modern suburbs, they also allowed low nuisance commercial properties to be interspersed with residential properties so that many of people's basic errands could be accomplished without traveling large distances.