What’s the usual amount of an in-app purchase vs the subscription price?

So when you’re using PayPal or Stripe to take credit cards, there’s the amount that Visa (or the CC provider) is taking, and then there’s the additional amount that PayPal or Stripe is taking on top of that.

For pricing a subscription that small, to limit (expensive) monthly transactions, I’ve seen a lot of companies do some variation of “buy 6 or 12 months and save” pricing strategy. - Something like $15/mo, but only $120 for the year.