I once had to pay a fee for using PayPal. I read through paypal’s terms of service for vendors and it said they can’t do that. I complained to paypal and they gave me 5€. The vendor continued to charge a fee for using paypal.

I surmised the vendor was bringing in enough profit for paypal to not penalize them and they just gave me five bucks to shut me up. Adventures in the world of capitalism I guess.