There's a different kind of registration for that I believe, I have a standard developer program license ($99USD/year), there's another "enterprise program" which I think can do 500: http://developer.apple.com/iPhone/program/apply.html
On the other hand... there's no easy way to charge. The provisioning profile is all that's needed to run the app.
Also, these profiles are intended for "internal distribution" (inside a company). I'm sure Apple will blow up your certificate if you try public distribution.