That's about 10x more that I'd consider reasonable for what is effectly hosting a static website and bulletin board. I think we've all just had our expectations blown out of the water by Steam (and the subsequent app stores).
I don't know how to respond to that. That's not a complicated thing to do.
Patreon gets to take the money they take because they've found a good niche, not because their website can do something that all websites have been able to do since the 1990s.
I personally think they take too much for what they provide. That's all. I am very happy they exist, though, because otherwise everyone would just be chasing the algorithm.
Does your static website and bulletin board also process the digital international tax schemes like EU VAT and liberate you of the legal and financial responsibilities of processing and filing each of the payments that you receive one by one?