Loenhardt estimates a cumulative cost of the Iraq war/occupation of $1.2 Trillion (New York Times). His estimate is on the low end, the high end is 2 trillion.
The list of what we could have done with that much money is pretty impressive, but it doesn't include things like funding the retirement of the boomers. I imagine that's even more expensive. In the meantime, we still don't have much inflation and our currency still hasn't cratered.
A trillion isn't what it used to be. The market apparently believes the future is rich beyond the dreams of avarice. Naturally we boomers can't help but think "why should the kids have all the money"? Which is why some economists argue we shouldn't sacrifice much to fix global warming, since the future can better afford the bill (and it's not so bad for the US anyway, compared to, say, Africa).
I think there was a Calvin and Hobbes cartoon about this. Calvin uses his time machine/transmogrifier to shift his work to future Calvin, but future Calvin is no more reliable than current Calvin. Things go downhill from there ...
PS. The Firefox online dictionary includes the word "transmogrifies", which was made up by Bill Watterson in his strip. It's not an english word. Good for them.