> Why do you think supply and demand do not exist in the housing market?
Why would you think that I think this? That's really confusing.
I think the issue you have here is that you are thinking in extremely simplistic terms and not really accounting for real supply and demand in this particular market. Instead of looking to Tokyo (which is a generally bad example because Tokyo and Japan are not great generalized models) you should look to New York City to see what will happen if you continue to build housing in the Bay Area. It won't get cheaper, in fact, the more you build the more expensive it'll get for a few of reasons:
Interest rates
Housing standards (environment, earthquakes, etc.)
Developers do not want to build low-margin housing so they'll only build "luxury" housing with cheap, but perceived higher-end finishes so they can charge more rent per sqft
Lack of available workers
As developers build additional housing they'll only build for higher rental rates, but because there is a near infinite demand for housing in San Francisco and California as a whole, as additional units come onto the market they'll raise the median rent, but it won't make existing housing cheaper, it'll just be the new floor. If you could build a million units or something in a year, you may be able to reduce prices, but construction doesn't work that quickly. Demand far outstrips supply and will continue to do so.
Tokyo is incomparable for a few reasons, but you can start by examining Japanese birth rates, immigration policy, and California's comparable car-only infrastructure.
Historical examples aren't very useful here because historically there were far fewer people, travel from the highly populated east coast to California was long and arduous and the benefits were "unknown", and people had a lot less money and stronger family ties. Trying to do global comparisons is generally suspect as well. But I guess if you want to see what things would look like, New York City, Hong Kong (pre commie China takeover) and the similar extremely high housing costs and density are appropriate versions of the future of the Bay Area real estate market. With that being said, who knows what will happen with remote work and the like, but probably won't have much in the way of price reductions there anyway over the longer term.
If you want less expensive housing you'll have to live somewhere else. That's just how the world works.