Yeah, that's the big "hole" in the model I'm trying to work out. How do you create some passive income off of the invested time and work creating the course material. This is why I am a proponent of the the 1 on 1 and "grading" model. It allows the students to get valuable feedback from their instructor. I can see well respected instructors in their fields charging quite a bit. Since it is all visible on the blockchain it's verifiable for students which could lead to real world opportunities.

It's also a great way for new professionals and instructors on Steem to gain a following. The one thing more valuable than a large payout is a quality follower. It would be worth putting in the work early even if the payouts aren't high.

Also, there are creative ways to "remonetize" work that has already been published. Revising some of the course material and running another workshop is totally possible, as long as it's altered or refreshed to some degree. You could also publish critiques of student work that could gain upvotes. The possibilities are there, but will require some serious collaboration, creativity, and trial and error, I think.