To be honest, I thought it would be in the 20% range, so 5% + processing fee sounds pretty good in comparison. From the perspective of funding software, I'm mostly thinking about indy game devs. Game portals can take up to 50% of the sale price.

From a business perspective, the processing fee is (I guess) incurred by the payee, so that's unfortunate, but I have difficulty thinking of a reasonable way to avoid that in any case. The 5% service charge that Patreon takes should be be an expense for you, as a business. Then you have to pay for marketing and advertising, so you're not going to walk away with more than 80% of the payment no matter what you do. At least you have the opportunity to directly balance the marketing/sales effort against the income (which is not something you can do if you are trying to sell through an existing sales channel -- they will advertise as much as they want and you will either like it or lump it). Patreon also gives a limited form of marketing by featuring projects in the newsletters they do, so that's a small benefit as well.

As a remote contractor that works in another country, I'm fairly well acquainted with bank charges :-P Most banks will happily charge you 6% for foreign exchange, and then still charge you $20 (plus a percentage) to transfer funds to another bank. It is (information) highway robbery. Like I said, 5% to actually provide a valuable service is refreshing.

P.S. For anyone in Japan, funnel all your money through a personal account in Shin Sei bank. You can thank me later. Not associated with the bank in any way, other than to be enjoying reasonably priced ForEx.

Edit: To answer your question, Tarn Adams has been sustaining about $7K a month from Patreon. He is likely an outlier, though.