That's probably "the cost of fuel, training for the entire crews/groundcrews, a whole bunch of munitions, enough spare parts to build two more planes, and so on with development prices amortized in and adjusted heavily for modern dollars to get the biggest number we could." The way lifecycles are, we've got birds twice the age of their pilots now. I mean, look at that billion-plus order from the Bulgarians for a handful of modern Vipers; they factored everything into that sale and it's insanely expensive. But they've probably got 40 years of use out of those aircraft...