Bloomberg Businessweek has an article about where the richest — and poorest — live in the America’s six largest cities and their environs. 
For Philadelphia the poorest live where you’d expect – North Philadelphia; Camden, N.J.; South Philadelphia; and University City.
The richest live in Dresher; Mount Laurel, N.J.; Sewell, N.J.; and Media. Frankly, we are surprised that Media beats out Chadds Ford or Wayne.
It should be noted that 4 out of 5, 6 out of 10, and 10 out of 15 of nation’s richest counties are suburbs of Washington D.C. Just chalk it up to the bounty of neo-feudalism.