Your first-principles argument is logically correct, but totally ignores the actual costs of living and salary in the given areas. The grandparent point stands just fine.
The first principles argument is consonant with my actual experience in the Midwest and SV. I have vastly more money left over after living expenses in SV.
Are you single? I imagine you find a reasonably priced small apartment for a single person in SV. I doubt you can find a reasonably priced 3000 sqft house in SV.