Yeah, that's a fair point. But Payright seem to have plenty of fees built-in to account for this - merchant fees (% of residual) + Customer fees (application, subscription and payment processing fees). Admittedly I am surprised by the success of BNPL schemes for small purchases since I've never used one and can't imagine doing so. I personally feel they're more useful for larger purchases. I'll be interested to see how they go.
