I would hope that the 10$ fee isn't just for a porta potty! I have been stopped by DOW once, before I even kayaked! I was flyfishing and I was only 13. But thats it. But again, if they would make improvements to the area (parking, actuall maintenence, litter control, and real bathrooms), I could see a 10$ a year, or like a 20$ a year park pass, but 10$ a day would be stiff, and I would probably not kayak the fork, and just go to shoshone becuase of that case.
My 3 cents, from DIA airport!