Having a DPT is not going to boost your income. My impression has been that attendings don;t really care what you did prior to medical school unless it is of some benefit to them (you have a PhD and ran a lab or something). The real advantage will in being comfortable interacting with patients, good hands on skills, and just having more general medical knowledge than your classmates (you know the different presentations of typical diseases). All that money and you probably will get little use out of it.