I would say the breaking point has already been reached. There are heaps of better places to live with a vastly lower costs. All we need to do is convince the VCs to fund startups in these places and we can all forget about SF.
And you need to make sure there's a big talent pool there, and good universities.
A few places are close to that, but it's not so easy to replicate.
This book talks about it some: https://amzn.to/2XAU3f0
And most of the places that are close have rampant NIMBYism problems of their own.