This seems to take a very inclusive account of government spending but maybe not so for the attackers. We may need to consider the recruiting costs and ongoing operation cost for years leading up to the attack - even for expenses unrelated to the attack but part of the support and growth that led to it. You could argue that every AQ expense upto 911 was in some way building towards that event. I think if we have such a broad account of the government spend, we should do likewise for the other side. But your point is still good.