Sure...
10 percent is traditional. Have a look around the local landscape to see how many "ten-percenters" there are, particularly in Lagos and Abuja, shadowy figures with lots of bling and a shiny Tokunbo with clear plazzie covers on its grubby seats but nothing much going for them but their connections.
Boeing is a bit handicapped by US SEC rules about bribery, sorry, commissions. This should apply to all companies traded on the US stock exchange and it can really put the mockers on Boeing and Bell competing with Airbus and Eurocopter, unhampered as they are by such rules.
You may occasionally be puzzled to read that Twangoland International Airlines has just torn up a contract for Boeings to go for (more expensive) Airbuses, when you can only scratch your head and wonder if it is so that the Twangonians are stupid people who cannot do their sums, or that the Airbus is so much better that it sells for a premium, or did someone just collect a very handsome commission, what we crudely call, yes, dash?
Sometimes there can be a great falling-out among thieves, when we get to hear what has gone on, after someone doesn't get his share of the booty. For now we can only watch and wonder.
By the way: Scratch that "finally." Airbus broke into the Nigerian market years ago with the sale of four A310s to Nigeria Airways. Get someone who knows the local airline scene to tell you how that one ended!