Oof, I should have put more details from how Evil Hat did their Patreon. The Patreon model I was thinking was not the flat monthly fee for maybe you get something model. That's a crappy model and only works for some stuff.
I was talking about the more Pledge-per-Item level. So, how the Fate World's Patreon works is that you pledge X$ for each product that they produce (to a maximum of one product a month). On months where you don't get anything, you don't pay anything. This provides a super simple way of budgeting for the producer. If I have 500 people who have pledged 5 dollars an item, 100 people who have pledged 10 dollars an item and 10 people who pledged 25 dollars an item, I have a budget of 3750 bucks to produce a splat once a month.
Basically, think of it less like a monthly subscription and more like a standing pre-order. You're saying that, "Hey, Catalyst, until I cancel this, if you make something, I'm going to pay this amount of money up-front for it." Since they know the funds are there, it gives them much more business freedom. Also, it has immediate reactions - if you put out crap, people cancel their patronage and you're back to standard business models - eg, wasting resources on PDFs.