Joseph Stiglitz, author of Globalization and its Discontents, tries to calculate an answer:
Shortly before the current Iraq war, when Bush administration economist Larry Lindsey suggested that the costs might range between $100 billion and $200 billion, other ofﬁcials quickly demurred. For example, Ofﬁce of Management and Budget Director Mitch Daniels put the number at $60 billion. It is now clear that Lindsey’s numbers were a gross underestimate.
Concerned that the Bush administration might be misleading everyone about the Iraq war’s costs, just as it had about Iraq’s weapons of mass destruction and connection with al-Qaida, I teamed up with Linda Bilmes, a budget expert at Harvard, to examine the issue. Even as opponents of the war, we were staggered by what we found. Our estimates range from slightly less than a trillion dollars (our conservative estimate) to more than $2 trillion (our moderate estimate).
If Stiglitz is right, then Bush has found a way to combine his disasterous war with his code-red economic mismanagement. That takes a rare talent, something you can’t teach.