The airliner price list is an interesting topic. As is common knowledge large customers get substantial discounts. Quite often the aircraft are then sold to a leasing company, who lease back the aircraft to the airline. Hypothetically there could be a substantial difference in the amount of the lease and the amount paid to the manufacturer, which can lead to some interesting accounting. The discount can be booked to profit or hidden in the price of optional equipment or perhaps (euphemistically expressed) paid in commissions, which might be the cause of some concern for senior management at Airbus right now. It might also explain why some airlines have such an interesting fleet mix.