I think you're right, there's no reason not to explain our fee on the frontpage, and just link right there to the help page that goes into detail (
update: added :)).
I'll also definitely add a csv export to the participants list, and do you mean some kind of mailchimp integration so you can send announcements and whatnot to your participants? That's an interesting idea we've thrown around a bit already.
As for Udemy's 30%, wow! Udemy is much more of a full-service sort of thing, it seems to me. More formal, they appear to do a lot of promotion and have a ton of community tools and so on. I think ultimately while both are about e-courses, they aren't really in the same market.