I suspect that that $90 billion was pulled out of thin air. Sometimes, I think that such dollar numbers are "super-sized" because, for some writers, everything needs to be exaggerated in a world with superhumans in it. Also, I think that the presumption is that such advanced tech just has to cost more. This was used as a plot point in the movie Batman Begins; Lucius Fox shows Bruce Wayne a prototype personnel armor suit that was developed for the armed forces; when Wayne asks why it wasn't put into production, Fox says that the Army wasn't about to pay the $200,000 production cost for each of its soldiers. (Of course, that eventually ends up as the Batsuit. Good deal that it just happens to fit the very muscular Wayne, eh?)