Sure, on the surface the numbers are impressive. Arlington's median household income in 2012 was $137,216. Loudoun County's was $127,192. Howard ranked #3 at $125,162 and Fairfax pulled up fourth at $124,831.
Dig a little deeper, and it's a different story to tell.
Median household income is the measure of ALL the incomes in a family living under one roof. That $127,192 in Loudoun County could very well be two earners bringing in $63,500 a year - about the salary of a mid-level federal worker. Or, two earners bringing in $48,000 each, plus a teenager with a part time job and an elderly parent with retirement income.
That's the reality for many, many working families in our area. The reason they live out in Loudoun County, Howard County & Fairfax County is so they have a shot at affording a home. (Sometimes called "drive 'till you qualify" in real estate circles)
According to the guys who calculate the official Cost of Living Index, when you factor in local costs like housing, utilities, groceries, and transportation in the DC area, the true spending power of these so called "privileged" households goes down by about 41%. http://www.coli.org/
Ask most "median income" families if they feel wealthy. The real truth in those big numbers being tossed about is just how much money, and how many jobs it takes just to keep a family afloat in an expensive metropolis.