This ended up being a bit of a ramble, but it's one (perhaps relevant) transplant's perception.
there aren't a ton of software jobs within the city, but there are many software companies paying DC salaries within a 30-60 minute commute to the southwest.
the cost of living in baltimore is also quite low, but many of the neighborhoods probably fall short of what your typical SWE would be willing to tolerate.
Being in Washington DC and knowing I can drive to half of those places in 30 mins, I wonder which metropolitan area definition the numbers in the article are using.
Does (NSA, SAIC, Ft Meade, NASA Goddard) really pay that much more than (Lockheed Martin, Raytheon, Northrup Grumman)?
Edit: Adjusted for cost of living, Baltimore > DC makes more sense.