OK, this isn\’t an all inclusive thing but it certainly can be argued that from hte point of view of the US the current wars in Iraq ind Afghanistan are incredibly cheap.
Nicholas Kristoff tells us that:
The U.S. will spend more on the war in Afghanistan this year, adjusting for inflation, than we spent on the Revolutionary War, the War of 1812, the Mexican-American War, the Civil War and the Spanish-American War combined.
Well, no, not really. The full paper is here. If you use only cash terms and upgrade for inflation, then yes. But you might rather want to upgrade for GDP (which makes the current wars decidedly cheap), or wages (less so).
But since we are talking about war we might actually want to measure by the value of a life.
A reasonable estimate of an American life these days is $8 million. That\’s what we actually observe people valuing their own lives at by the wage premium they demand for risker jobs (actually, that\’s at the high end of estimates but still….).
WWII deaths for the US, military only, were 416,000. That\’s $3.3 trillions worth of lives.
Afghanistan and Iraq have so far led to (over a slightly longer time period) 5,800 US military deaths. $464 billion.
As ever, whether something is expensive or cheap (which, please note, is absolutely nothing at all to do with sensible, moral or desirable) depends upon what you decide to measure.