Patreon has different plans which take anywhere from 5-12%. On top of that they charge payment processing fees and bank transfer fees. In terms of service you are getting nothing but a profile page. A flat 30% fee is considered standard for most online marketplaces.

Considering how much more complex and expensive video hosting is, and everything else YouTube offers, I don't think a 45% cut is unreasonable. In fact YouTube does have direct paid channel memberships (which is a much closer business model to Patreon), and for that they take 30%.