US taxpayers are paying $80B initially for war costs and probably much more later on as reconstruction costs

Iraq's current oil revenues stand at about $10B per year. If the US were even able to get a 50% monopoly over those oil fields, it would take 16 years to just finance the initial cost of the war. The additional bill of reconstruction could take 3 times longer to show returns. And by that time, Iraq probably wouldn't have any oil left.

How can the US possibly economically benefit from this war??