Most people like to live in the nicest place they can afford. This is a force pulling prices upward when many people with excess cash are competing for a limited supply of homes. Its why you'll pay more for the same size property in a wealthy neighborhood.
> Why are prices for an apartment in SF only 3k/mo instead of 30k?
Because some people in SF can only afford 3K/month. But if you added 3k/month to literally everyone's income, that number would increase.
(In case you're wondering why the many people with more than 3k/month don't crowd those people out: the wealthy depend on those 3k/month people for labor. At least for now.)
No, because local wages cannot sustain those prices
If local wages could sustain those prices, then yes all rents would rise to that new higher local income level
That is (quite self-evidently) prices are so phenomenally high in ultra high-income areas like SF
Every single landlord is setting prices by the same metric: what can the people who would live here be able to afford? Competition between landlords is almost nil, which is why you find almost no "deals" anywhere. The market is totally efficient. Everyone agrees on how to set prices: by local wages.