They are pretty close, and Philadelphia is a big city. If you are referring to the southernmost border of Philadelphia, like the airport or sports complex, halfway would be right around the PA/DE border. However if you're referring to northeast or northwest Philadelphia, the halfway point would probably be somewhere around Chester or Flosom or Brookhaven, PA.
Batley
One halfway point between Augusta, GA and Lancaster, PA is Shockoe, VA.
The halfway point is Saint Marys, Pennsylvania.
Columbia sx
Rutledge, GA
Estesburg, Kentucky.
The city that is the halfway point between Charlotte, North Carolina and Delaware is Dinwiddie, Virginia. This town is the exact halfway point.
Harrisonville, PA
Lancaster, SC.
Gretna, NE
Allens Corner, NJ
Halfway point between Wilmington, NC and Asheville, NC?