Earlier quoted context omitted.
Also known as supply vs demand... Bay area is infamous for many housing supply constraints in regulations. As far as loans increasing the demand side, banks can be pretty strict with %20 down payment restrictions. Which is why once houses go out of the dual income high earner price range ($1-1.5 million), you start seeing it overflow to other less desirable regions in the bay area.
But the creation of credit costs nothing therefore rent extraction can scale up to match productivity gains in a heartbeat.
it has not happened yet but it is certainly pricing many out at lower ends of the income scale.