I don’t think that many enterprise customers are going to want to use PayPal (if the past decade is any indication).
I think it would take $2000 to $5000 to develop something that worked at all, and likely twice that for something with more features and proper specs and tests.
I have a handful of customers that pay with PayPal, so I’m considering looking at trying to pull in into about existing subscriptions sometime so I might know a little more soon.