... it was to offset the costs of the payment processor, which if you've never had to deal with the likes of Visa, Amex, and Mastercard, generally is between 2-5% of each transaction. (i.e., every card swipe)
You might have seen the 'minimum order' signs for some small businesses, like that one Chinese take out place that delivers to you, but wants you to order a minimum of $15? That's to make it worthwhile, and cover some of their fixed expenses, like the aforementioned transaction charge, paying the driver, etc.
And while a lot of gas stations no longer do it, a lot of them had a higher price for gas if you were using a credit or debit card, in order to make up for that transaction charge. Gas is one of those things that is literally a 'I made 1 penny per gallon sold' type of margin, if that.
Don't get me wrong- I don't necessarily agree with the way that Patreon made the announcement, or what the end effect is on both ends. There are a couple different ways that they could have done it, along with maybe giving people more time to digest the information. (It's December 7th, and the new policy kicks in on the 18th? that's roughly a week and a half- some people take longer than that to decide that they need to think about changing process...)
I'll wait and see what Doc want's to do- it's his show, after all. I'll cheerfully up my support level if it helps any- I'm in a slightly more stable position financially now then when I started.