Apple should be able to demonstrate the investments they have made and get other companies (like PayPal) to pay a reasonable fee, like 10¢, for each transaction their customers enjoy. Not that complicated.
On the flip side, those other companies need to guarantee that there will be no malware from using their software, and they should make their, and Apple's, customers for any crimes there customers suffer - including reimbursement of financial losses.
I think you misunderstand how this works.
NFC is just a wireless "port". Your phone connects to the NFC terminal and then the software conducts the transaction over the wireless link. This is very much the same as swiping a credit card or inserting a card into a chip reader, only wirelessly.
Charging for this would be like Apple deciding that they can make you pay to transfer a file over Airdrop, and blocking it is like deciding that their phones will only Bluetooth pair with Apple Airpods and no other headphones.
Deciding that their own payment service is the only one that is allowed to use the wireless link (in an attempt to block other payment services) is just scummy, Microsoft-esque behavior and deserves to be slapped down.
Apple is not entitled to be the only wireless payment option because they design/build the iPhone hardware, in the very same way that Microsoft is not entitled to be the only web browser because they designed/built Windows.
There is no defending their conduct here.