Where do you think its coming from now?
As far as the Bay Area goes it appears to be trickle down from FANG stocks buying up VC backed companies and the associated recycling of those proceeds into new ventures. There's also a bit of China money buying up single family homes, but China has been putting steady pressure on all that trying to plug those foreign exchange leaks, so if anything that's waning.
Where's the money for the stock market coming from? It used to be quantatative easing and FED reserve bond buying. I guess the yen carry trade in part and probably lately tax cuts a bit. It's harder to see where the money is coming from in the stock market though because buyers are largely anonymous.
[1].http://www.calculatedriskblog.com/2018/02/new-home-sales-dec...
I would personally add Russia to the mix. The reason is simple: both China and Russia are sources of capital flux, where those with means are funneling funds outside their respective countries.
Because there are, or have been, capital controls in place, those who move money out of their countries are willing to pay a premium for it. Funnily enough, there is a name for the phenomenon where actors with money are willing to pay exorbitant transaction costs in order to move funds from one jurisdictional domain to another.