Not directly related to paypal - the big (humongous) credit cards changed the rules several years ago - think it was 2018. A lawsuit was settled, and the Visa/MC lenders agreed it was no longer prohibited for vendors (e.g. restaurant or comic book store) to add a surcharge (generally 3-4% based on the credit card fee imposed on the retailer) for customers who used plastic. Or, alternatively, for those retailers to offer a cash discount for cash-paying customer by the same few percent.
Paypal not being party to the settlement can do whatever it wants, but it's policy is now firmly outside the practice of remainder of payment-card system.
It caught my eye when I went back to hell, I mean home, in NY, a few years ago when all the gas stations offered a cash discount or credit card surcharge. And it seems like all the other retailers joined in the policy, too. The poor slobs, I mean my family and friends still living there could give more precise info.
But I've also since noticed some restaurants in Texas have adopted the same policy, and also saw a gas station that does the same (only it had a dime difference between cash/credit price though, not a % based amt like the rest I've mentioned).