But that is not actually what happens in the cities like SF. The lowest tiers of housing are not affordable. The worst apartment I've ever lived in my life (inc

But that is not actually what happens in the cities like SF. The lowest tiers of housing are not affordable. The worst apartment I've ever lived in my life (including Soviet-built flats) was in SF - a crappy 1906 victorian (or whatever you call these ugly hovels SF is full of) subdivided into 6 units; drafty, not updated in ages, no dishwasher or laundry, etc. It was also the 2nd or 3rd most expensive rental per sqft in my life (the only other ones were also in SFBA). I took it because I didn't even realize apartments SO crappy can exist, e.g. I didn't realize there was no dishwasher until after moving in... and the whole neighborhood was like that. Normally, that would all be "lower tier" housing. In SF, it was $3k/mo in 2014 and rented to either techies, or roommates (sometimes 2 unrelated people per bedroom). If someone built luxury towers in the same neighborhood, the techies would have moved there and actually made the lower tier of housing somewhat cheaper for others.