Actually, Stripe's market is smaller than Square's. But these business models will never capture a large percentage of their respective markets anyway due to the high rates (negotiating with an acquirer can get you almost 50% less than their rates). After all, "Simple Pricing" is not as good as it sounds. Why pay 2.9% on a 0.05% debit card for the sake of simplicity? I'm sure Excel can handle these variations. This is an unfortunate consequence of the inefficiencies of that industry.