The Bush admin was famous for making war expenditures ‘off budget’ items. There is the CIA budget which is always a question. How much is taxpayer funded and how is is covered by their drug ops? Remember when it came out that we were bribing the Taliban not to attack truck convoys in Afghanistan? What accounting category is bribery? This estimate is no doubt conservative.
Nevertheless, the Brown study notes that its “estimate is also conservative,” adding:
This report has not included here state and local government expenses related to medical care of veterans and homeland security. Nor does this report calculate the macro economic costs of war for the US economy. And while this report discusses some of the ways that families bear the burden of caring for seriously veterans [sic], I have not added a value for the costs of their uncompensated care.

