I think for a lot of jobs - medical profession, engineering etc. the marginally higher salaries here in no way compensate for the much higher cost of living.
This has been our experience living in the District, Seattle and Minneapolis in the past 15 years. Yes, you make 11% more as an IT professional or federal lawyer in the "Washington statistical area" than you do in Minneapolis. But that in no way makes up for the 78% higher cost of housing, auto insurance, preschool/daycare, and a few other big ticket items.
I suppose if you are comparing a housing development outside of Frederick, Md. or Leesburg, Va, to Minneapolis or Seattle proper, that 78% gap closes to 24%.
But then, you're living in a tract home in exurban "Frederick County, Md." vs. a city.