ha! I've got to think that his numbers have dropped dramatically just from moving to the app.
There is actually a historical example from early on in podcasting to learn from. The Ricky Gervais Podcast had massive listenership in he millions (especially since this was mid to late 00's), switched to a pay model and got <10k people to pay for the podcast from what I understand.
I think there's some merit in trying to get podcasts onto concentrated platforms and production umbrellas for advertising reasons, but pay models seem to never work.