That wasn't the plan. The plan was that we'd do absolutely everything for them, not just hosting. For example, we'd build whatever features they needed, such as tools for deep analytics of their user base; we'd do all their social media marketing; we'd run their events, job boards, etc; we'd spend a great deal of time working on providing eyeballs and on working out how to monetize their traffic.
If we had solved these problems, 20% would have been a very reasonable cut I believe.
Your post reminded me of when I tried to monetize "blooks" (serialized books in blog format) about 5 years ago with PrintPusher.com (now defunct).
It was a tonne of work. Sourcing and promoting the content, publishing and layout (we were using WordPress, which was way jankier back then), and yes, generating traffic. It was so much work I didn't have time to enjoy any of the content, and it became unfun.
Heck, you should've just asked me. I could've saved you the hassle ;-)
If we had solved these problems, 20% would have been a very reasonable cut I believe.