> I'd guess that the people worth $600,000 Facebook salaries are already living there and working for Facebook.
Yes! I think this is true. However, the more interesting development to me is what happens 10 years from now. The engineers who are making $600k in SF are typically 10 years into their career (if not more). This is the biggest knock against expanding into places like Omaha- there's plenty of entry-level talent, but little, if any, mid-level to senior talent.
In Edmonton (Canada), where I'm from, there's an awesome university that graduates tons of CS grads who immediately head to the Bay Area, because they can make 4x more there. As such, most of the work in town isn't sophisticated- there's lots of web development shops, but not many jobs doing sophisticated engineering at the level of, say, Facebook or Google.
As a result, you're right, there's not many people who could get a $600k offer from Facebook. But! If these companies start supporting remote work, we could see tech ecosystems developing, and we could see new grads staying in these places, and building ecosystems around them.
To answer your question about:
"why, if there were such big savings on the table, these companies hadn't already moved in this direction."
I think the answer is as follows:
1. New grads need more experienced talent to help mentor them and ensure that they're seen as productive.
2. All of the companies' offices have historically been in certain locations, so we either need to a) have the new grads move to somewhere we have experienced talent, or b) need to have experienced people move to where the new grads are.
We see both of these- companies regularly will start new offices once they can get sufficiently experienced people to move there, but only when they can get that. This is the main reason (aiui) why many of the large tech cos in the Bay Area are concentrated in the Bay- there are no senior level people who are interested/willing to move.