Traveling from Tampa, FL to Baltimore, MD?

I'm trying to find a cheap way to travel from Tampa, Florida to Baltimore, Maryland and back again for my son and myself. Driving by car takes a toll on my body plus it's not really cheap...approx $135 one way. Train and bus are very expensive. Once in a while I can get a cheap flight but varies. I'd be willing to hop on this and skip to that if I could do it inexpensively. Does anyone know of a commuter train, plane, bus, boat, van...any cheap way to get back and forth?