The costs of
a bad hire are overstated. The cost of systemic bad hiring may grow geometrically. If that estimation is correct (bad hires result in more bad hires) then
no price is too much to avoid a bad hire.
And consider the US Air Force. They have an unlimited number of young people willing to learn to fly jets. Qualified candidates even. So they can filter any way they like, and still not run out of applicants. So their filters seem capricious, because they sometimes are. And it doesn't matter.
Is Silicon Valley in that position? Depends upon who you are. I don't think Google for instance is running out of candidates.