At first I only charged $12/month or $96/year. As the library of screencasts grew, I raised prices to $15/month or $135/year and I'll probably raise prices again pretty soon. So far, it's been slow, steady growth and nobody has unsubscribed.
I think a key thing that helped me is that I made very different content from the other Elixir screencasters. They all focused on short, highly-edited content that taught specific language features or small libraries and I chose a project-based approach where I introduced language features as needed and videos sometimes reached nearly an hour. It made my service a bit less of a rival good to the others and instead something that people might buy in addition to one of my competitors.
In 11 months of 5-10 hours a week, Alchemist Camp is covering the rent and it's also lead to me meeting a few famous Elixir devs, including José Valim! Definitely a fun indiehack and I'm glad I'm doing it.