It's not easy to buy up entire blocks of houses. You get hold-outs, either people who understand that they're in a position to block a potentially lucrative deal and get a big payout, or just people who have a sentimental attachment to their homes or whatever.

The idea that there's a lot of elasticity to the construction trade is also naïve. Construction workers from "all over the world" can't move here -- we have an immigration process, and it's not one that's favorable to construction workers. We are also in an area that is itself not very conducive to living on a construction worker's salary.

And also, who are these developers who are so eager to build high-rise housing in a market that is stipulated to have affordable rents? It's a big capital investment to build a modern skyscraper, especially if there's a construction crunch, especially if you have to do things like buy out large areas without the benefit of government coercion, especially if there are similar projects going up across the city to compete with you. Housing is not typically a highly profitable use of real estate to begin with, and San Francisco is also a city that is not very landlord friendly.

This dream of in-fill development being a simple cure-all to San Francisco's housing ills like most "one simple trick to fix all your problems" -- click bait, not a real solution.

None of this is to say that SF shouldn't have in-fill (it should), or that SF shouldn't reduce barriers to development (it should). But be realistic. Unless you rewrite everything about SF back 50 years, it's not going to dramatically change everything about this city overnight.