I'll throw in my $.02:
I received my MS from ASU (which was the top-ranked graduate Exercise Science program at the time, tyvm) 7 or 8 years ago. Damn, I'm old. Anyway, I would certainly count my time there as worthwhile, but not necessarily directly leading to my making more money. The fact that I have letters after my name doesn't make me a better trainer. Although the same could be argued about certifications--I've met plenty of certified personal trainers that couldn't coach their way out of a wet paper bag.
That being said, the knowledge base that I developed while there has been invaluable. Not only the classroom info, but also just interacting with a lot of REALLY smart and passionate people. I had many informal discussions with other students and/or faculty that really shaped my ideas and approaches. Sort of like this forum, but with actual beer. Having the academic background enables me to evaluate and integrate new ideas and training theories more effectively. I think I have a greater appreciation of the how's and why's than the average gym-goer.
I wouldn't trade the experience, and if finances permitted I would love to go back and get a PhD.
BUT, I'll be the first to admit that I've learned more practical, applicable, info from Mr. John and Mr. Wolf than I did from school. Being introduced to CrossFit shaped the way I do things. From a day-to-day perspective, the alphabet soup after my name doesn't really seem to affect how much money I make.
Robb and R. Alan both have great points--consider well where you want to end up, and then choose your path accordingly.