best way to monetize nfc payment app.

[Windows Central Question]

I haven't found an nfc payment app similar to apple pay or android pay on their respective platforms so I made one. I could use ads(doesn't appeal to me much, because wouldn't see much profit I don't think). I could charge for the app, or I could setup the service to where they pay me 0.5% at the end of the month for whatever amounts are processed using the app. None of these seem perfectly ideal to me. Which of these, or others can you all think of to monetize the app, without ripping people off so to speak.