Well, sort of. It's forgetting taxes, house prices, and more.
Places where you can buy decent stand-alone homes for $50,000 and/or have no state taxes are rather different from Mountain View and Manhatten.
It's funny how people in the pricey places look at a $100,000 salary and not see how it is, all by itself, plenty to support a large family in a home with a big yard. People living that life look back at the city folk and can't imagine how they could ever afford the same thing in a city -- it'd be roughly $2 million (a factor of 40) in San Francisco.
Folks who work in the DC Metro area probably make a good bit more than that.
I'm not actually involved in hiring, just recruiting and trying to find good engineer candidates.