you can’t build to infinity when everything is built out…
But the impression I often get on HN is that you've got people making well above that finding themselves barely able to afford a place to live in SF.
I'm clearly missing something, but what?
It's an indictment of any system that people making twice the median household income cannot afford to buy housing within a reasonable distance of wherever their labor generates that income. It's a terrible situation - communities in which at least half of the necessary jobs do not pay enough for the people who do those jobs to live in the community - and it isn't good for anyone in or around those communities, and probably not for the nation as a whole.
The fact that, yes, yes of course there are other communities where the economics are different doesn't in any way mitigate the fucked-up ness of the situation the GP is describing.
The only homes I've seen for $200k need to basically be torn down and are too small for a family.
That's much less true of most metros. Even a fairly expensive city like Boston, while there are expensive suburban towns, an hour drive gets you to some small cities, exurbs, and other suburbs where housing prices are--if not cheap--pretty reasonable (e.g. $300-400K for midrange houses--though prices may have risen). And a lot of the professional jobs are well outside the city anyway.
An hour or so commute each way sucks, but if you can get a Bay Area job that is either fully WFH or that only requires you to come into the office once a week being an hour away wouldn't be too bad, especially if you can arrange the hours on that one day a week you come in so that you are't driving during the most congested times.