Being part of the new type launch customer programme it would be reasonable to expect the RFDS got a 'Honeymoon' deal on the purchase price. A common benefit for a new type into a country.
The operating cost of the aircraft should not be a variable; I would assume there is a smart group of people at RFDS and as such they would be paying Williams TAP/Elite for 'power by the hour' and the top programme includes overhaul, repairs and rental engine. So no outlay other than the hourly rate. The Avionics would be covered under a similar programme. The airframe has a warranty attached to cover anything other than 'fair wear and tear'.
So why are people bitching about the operating costs? The only variable would be an unpredictable fuel cost depending on where the uplift is made.