Almost, except that progressive taxation significantly advantages low-income-low-COL. The $145k earner will pay more than proportional taxes, so will need lower than $145k expenses to achieve that $5k surplus.

Lenders also don't seem wild about letting you commit 80% of your take-home to a mortgage, even if your discretionary cash after the mortgage would be the same as in a cheaper place with a mortgage at 25% of your take-home.