I think this is one of the problems flattr tries to solve. instead of multiple micro transactions you make one larger transaction each month to flattr, who then divides it up to all the creators you want to support. I don't know how Patreon does it, if they make one charge for each creator you support I guess the transactions fees can become a large part of the total amount.
All patreon customers are also only charged once per month no matter how many creators they support. The main difference being that since Patreon has people pledge specific dollar amounts instead of trying to figure it out month-to-month like Flattr the average Patreon customer has much fewer creators.
https://flattr.com/