Surprising that they would choose not to take a cut of sales, as it seems like a natural opportunity to earn some revenue. Then again it might make people more willing to get started and then find themselves needing the Pro features further down the line.
It is also technically far trickier to do all the payment processing and take cuts and make sure everyone is paid and happy. This way they can let Paypal/GC do all that work and focus on making a great product.
