It is easy for a thousand engineers to train in Bay Area and move elsewhere.
But could another locale train a thousand engineers to be ready to employed in the Bay Area companies?
In many cases, the value (initial value) comes from assimilating in the culture and while a lot of bigCos could still make people work in Bay Area before sending them home, the challenge is for these locations to evolve to be capable themselves.
This forwards an over-inflated notion of the cultural and knowledge value that working at a Bay Area company imparts.
The Bay Area does not have a monopoly on good culture or experts: at times it may even notably lack them. There are many experts there and much good culture to learn from, but there are also many idiots and charlatans, and it is just as likely you'll find one of them first. How does a beginner tell the difference?
There is no locational bound on where people can learn to write great software, on where they can write great software, on where they can teach others to write great software, or on where a strong culture can be grown and shared, i.e. one of good ethics, responsibility, fun, art, innovation, trust, etc.
The Bay Area is not magical; it is just a place where a lot of money and a useful attitude toward spending it (on risky technology ventures) got cyclically concentrated over time.
I believe most Engineers in the Bay Area did train somewhere else. California has 1/4 immigrants from other countries, and some similar amount moved there from other states.
It is easy for a thousand engineers to train in Bay Area and move elsewhere.
But could another locale train a thousand engineers to be ready to employed in the Bay Area companies?
In many cases, the value (initial value) comes from assimilating in the culture and while a lot of bigCos could still make people work in Bay Area before sending them home, the challenge is for these locations to evolve to be capable themselves.