The cost of my education is and will be nothing short of immense (loans). My classes aren't always amazing. Still, I hadn't anticipated the full value of my choice to come back for that technical degree. You don't just go to school to program or do homework. There's much more to it than that. A huge part of it is networking and peer collaboration. There's that old saying that if you look around and you're the smartest person in the room you're in the wrong place. My professors are incredibly networked and have brought me internship and job leads I couldn't have found on my own.
Also, I'm in comp eng, which is typically more of a hardware degree. I could have done CS, but I ended up in eng for a number of complicated reasons. Still, you mentioned the hardware thing in a comment, and I've found great value in studying some hardware. The ability to talk from high level language through gate level implementations is valuable knowledge.
I think the other thing to consider is the state and future of this industry. Naturally, it's incredibly bright, amongst a sea of industries headed for the garbage can. More and more, the masses will be flocking to where the jobs are going. I think the formal education might be helpful in this sense.
On the flip-side, you seem like you are already on your way. Nobody would not hire a candidate with ten years of real experience due to the lack of degree.
If I were in your shoes, it would come down to cost and networking. Can you finance it well? Will it give you exposure to people and places that will greatly accelerate your career?
Of course, I still believe in liberal arts and creativity, so there's also the whole education for education's sake argument :)