We're working on a search engine for online courses (classpert) and the subscription model was always a big question mark for us. We try our best to show advantages of the subscription but for the end user, we're not so sure it's the best model (and we doubt providers really believe that either). Personally, Udemy model (pay per course) works better for the general case, and I would only subscribe to specific content made by specific, top-notch people.