Northern Liberties has plenty of bars serving great food at great prices within a few blocks. There are also a few excellent BYOBs [1] and a fantastic tapas joint.
In general, the prices are lower, the vibe more laid-back, and the scene a bit more bohemian than in trendy nearby Old City.
Links:
[1] http://www.moon.com/destinations/philadelphia/restaurants/bring-your-own-bottle-0