It happens every now and again on here: someone comes up with like a 2% improvement in aerodynamics, and people are unimpressed. Meanwhile airlines are basically scrambling to get it rolled into their next-gen purchases because it's the biggest improvement in costs in a decade.
You cannot possibly know that without knowing the operational lifetime of a plane and it's expected return. An airline doesn't buy a plane planning to break even on the purchase cost, for example.
Setting aside that you pulled that number out of your ass to argue against it, if something produces 400X it's purchase cost over it's operational life time, a 2% improvement takes that to 408X it's purchase cost for only a 2X increase in initial outlay, meaning it pays for itself 4 fold.
But very few innovations have that sort of effect on manufacturing cost to start with.