The border can be really thin.. In your case i guess you would need to tweak your business model to dissociate your app (that you would be give away for free), from a service outside the app (that would be sell for 100$/month) The app would react differently if you are registered as a 100$-a-month user or not
you may have a look at companies that use freemium business model such as Vimeo or Spotify (same app, monthly fee for getting more from it)
See this thread on Quora : http://www.quora.com/Apple-Inc-2/How-does-Apple-define-digital-content-when-taking-its-30-cut
The border can be really thin.. In your case i guess you would need to tweak your business model to dissociate your app (that you would be give away for free), from a service outside the app (that would be sell for 100$/month) The app would react differently if you are registered as a 100$-a-month user or not
you may have a look at companies that use freemium business model such as Vimeo or Spotify (same app, monthly fee for getting more from it)