When demand for housing (or any other product) exceeds supply the price goes up.
The system SF has is actually broken due too to much regulation. Regulation that inhibits the creation of new housing which would increase supply and lower prices.
SF and NYC are "desirable" places to live. People want to be there. The world is more "globalized" than ever now.
How does supply and demand cope when 6 million to 60 million superhumanly rich people (from all over the world!) want the same thing a non-superhumanly rich person also wants?
It's the exact same "superhuman AI will take all our jobs" reasoning, except in this case we have actual humans with access to vastly more wealth than any average person can accumulate.
On a long enough time scale, the market may win and only $100 millionaires and billionaires will live in SF and NYC. But for now, the non-independently-wealthy (those poor suckers who need a 'job' to live) end up paying $5,000 per month for a one bedroom apartment. That means you need to make over $200k per year just to be independent. In reality, you should be making $450k per year to live "nicely." (In actual reality, if you are a programmer who can create value with your mind your skills are easily worth over $3 million per year).
Regulation could give us options like: no non-resident foreign nationals may purchase property here. nobody may purchase more than one housing unit within the city limits. no one person may be the landlord of more than 3 housing units (or else you have "the rich get richer" where one guy uses rent income to buy more buildings to get more rent income—soon, one guy has 60 buildings being milked for rent). nobody may purchase units for money laundering purposes. hell, throw in a morality clause and say if you are convicted of a crime you lose your multi-million-dollar condo as well (hi, wall street frauds).
Regulate the heck outta the housing market because fixed assets can't be efficiently allocated in the face of supernormal resources unless you consider "the rich deserve more than people with full time jobs" to be a proper way of allocating physical pieces of the planet earth.
You are appealing to supply and demand as if it was an immutable law of the universe and not just an outcome of predatory human behaviour.
When demand outstrips supply, prices go up. He never suggested otherwise. But why do sellers raise the prices on necessities such as housing just because they can? It is because they are predatory assholes.
And why blame just the property owners? Presumably if no one was willing to pay the rents they would have to come down -- but some "predatory" renters are willing to pay to get what they want.
However, I think that a renter who pays an exorbitant rent when a cheaper yet still liveable alternative is available is partly complicit.
I work for myself, but in the hypothetical situation where I worked for somebody else, no, I would not offer to take a lower rate from my employer just because it is more than I need. I am entitled to every single penny that my employer makes from my labour. The difference between what he makes from it and what he pays me for it is capitalistic exploitation. It is in the interest of justice that it be minimised.