Of course, if you really do the math, even beyond being unsustainable from an economic and infrastructure/governance standpoint, on a personal level, owning and maintaining a house in the suburbs has many hidden costs.
If we lived in the city, it'd take ~2-2.5x as much money to buy a house with one fewer bedrooms than our current 'burbs house has (two of our kids could have bunk-beds I guess) and probably 500-100sqft smaller overall and in kinda so-so shape, and that's outside the heart of the city and not in a ritzy neighborhood (but also not a slum). Then we'd also have to hope our kids got into one of a couple good waiting-listed charter schools, or else pay another $2-3K/month for private school. We couldn't afford that at all, and even if they got into the charter schools we'd be living like paupers thanks to the much-higher mortgage (or rent).
So, lifeless, boring 'burbs full of seemingly-intentionally-ugly houses it is.
There's also a definitions thing hiding in here: much of San Fransisco is pretty damn suburban, with houses, one or two story buildings, etc. Still expensive as hell, though. And then look at all the towns on the peninsula. I'd argue that the affordability differences are regional much more than urban/suburban driven.
Worth also looking at the costs within those regions of city vs certain suburbs, like SF vs Palo Alto, or LA vs Santa Monica.
[0] such as https://www.washingtonpost.com/news/business/wp/2016/09/13/m... http://www.marketwatch.com/story/do-pets-have-the-potential-...