ardour.org makes the majority of its income (approx US$200k/yr) via a PayPal micropayment account. Most of our transactions are < US$12, the crossover point where the standard and micropayment fees are the same (higher amounts are better with standard fees). On a US$1 transaction (we do thousands of these every month) we save 23c per transaction.

The one downside is that if PayPal ever stops offering this, the revenue model for ardour.org will have to change, since there are really no viable alternatives.