Best way to implement payment system for a Realm App?

I’m currently having a problem in finding the best way to implement a subscription payment solution for my SaaS product, so has anyone any recommendations and already done it with Realm?

I’m considering Chargebee, but it can get expensive. Also, I thought about implementing every payment solution I need myself but maintaining that is not something I want to spend time on.

Would love to hear if someone has a recommendation for me. Thanks