Fair enough, but I already acknowledged zoning to be a (local) factor. My point was that it doesn't explain unaffordable homes in vast parts of the world.
You've taken the most notorious large city in terms of zoning but that does not represent the entirety of the issue of homes being absurdly expensive across the board. Which is not a SF issue, it's a widespread issue. Zoning doesn't explain the wider issue.
In the Netherlands, 400K would typically be the value of the land + construction combined. The land is often owned by the municipality, then to a developer, and this is the municipality's #1 revenue stream.
Regardless, 400K is unaffordable to the vast majority of people.
1) It's extremely difficult to get approval for new housing
2) There's a large backlog of developers attempting to build new housing
...which should convince anyone that regulation is the binding constraint, not a lack of willingness to build.