That's the part I didn't get: he says he wrote this to replace three different processors. If Stripe is a payment processor, what exactly did he replace?
Compared with Stripe's 2.9% + 30¢, it's expensive, but Gumroad appears to do two things that Stripe doesn't:
- Work out whether and how much sales tax to charge (which I guess should be easy if you operate in only one state)
- Absorb chargeback fees
This second one makes the 5% seem more reasonable.