I doubt that prices lead to brain drain. Sure there is a guy or two who will walk away. But I know more then a few people who are like: more then 2/3 of my pay to live in the city? No. Problem! Living in the city is super important!
I've seen it first hand with incredibly talented people that hated living in the city. There are plenty of tech hubs elsewhere. Sv isn't special. 2/3 of your pay is a bad decision unless you are being paid 600k+
