But the salary differential between top engineer in the Bay Area vs. top engineer in the Midwest is more like 2-3x than 10-15x.

I’d say smaller than that. Working in Pittsburgh there are plenty of folks netting Bay Area comp packages (180K+ base salaries, 100K+ stock grants, big bonuses, etc). I don’t think the point of opening a Midwest office is cheaper engineers, but the ability to tap into local expertise cocentrations (robotics and AI/ML in the case of PGH).

OK, it's not 2-3x. Especially if we're talking salary.

Salary for a top individual contributor engineer in the Bay Area (full stack), outside of specific skillsets like ML/AI, will top out around $200k.

Midwest, someone with the same skillset would probably make $125-150k.

this is not true for TC at all, case in point see levels.fyi. $200k is basically one level above a new grad at some of the higher paying, well known companies

I was referring to salary.

I'm looking at Levels.fyi and at Google you only start to break $200k salary at L6 (Staff Engineer).

Total comp in Bay Area is often around $300-400K. That includes generous equity though, so may not be relevant when talking about startup salary affordability.

Often? Seems like $150-200k is closer to the norm.

For FAANG I'm pretty sure it's in the $300-400K range. If you include all tech jobs (including startups and old-line jobs at eg. IBM, HP, Oracle, National Semiconductor, etc.) I could see it averaging out to $150-200K, but only because the previous-generation companies don't give equity and equity in many startups is worthless. The flip side of this is that if you pick the right startup (AirBnB, Lyft, Uber, Stripe, etc. when they were startups), your equity is worth millions.