I mean we don't get to see how much our supermarkets mark up a bottle of milk or a packet of cereal from the price the manufacturer sells it at. Likewise we don't get to see how much Apple's slice of the pie is within the advertised price (although it's no secret that it is 30%).It's exactly what apple is trying to hide. They won't let developer to even show some note about apple's cut. They doesn't pass such applications in App Store.