DoD contracts may be lucrative, but when your custom navigation-and-communication software package for fighter jets FAILS just because you crossed the international date line the wrong way... that's going to be costing somebody some serious cash. Even a Homer Simpson-sized "Doh!" won't cover that kind of oops.

Software Bug Halts F-22 Flight (Slashdot)

It would've been even more expensive, I imagine, if these were unmanned flights... Now, I'm not going to publicly confess the dollar cost of the biggest technical gaffe that I've been personally responsible for, but it wasn't quite as big as this leetle F-22 glitch. I will posit, though, that I suspect it's much harder to quantify the real impact of most software bugs in terms of dollars.