Costs of Wars

According to a paper titled "The Economics of the [American] Civil War" by Roger L. Ransom of the University of California, Riverside:

"The Civil War has often been called the first "modern" war. In part this reflects the enormous effort expended by both sides to conduct the war. What was the cost of this conflict? The most comprehensive effort to answer this question is the work of Claudia Goldin and Frank Lewis (1978; 1975). The Goldin and Lewis estimates of the costs of the war are presented in Table 3. The costs are divided into two groups: the direct costs which include the expenditures of state and local governments plus the loss from destruction of property and the loss of human capital from the casualties; and what Goldin and Lewis term the indirect costs of the war which include the subsequent implications of the war after 1865. Goldin and Lewis estimate that the combined outlays of both governments -- in 1860 dollars -- totaled $3.3 billion. To this they add $1.8 billion to account for the discounted economic value of casualties in the war, and they add $1.5 billion to account for the destruction of the war in the South. This gives a total of $6.6 billion in direct costs -- with each region incurring roughly half the total."

A historical inflation conversion chart from Oregon State University show that 1 dollar in 1860 would equal to $23.25 in 2006. (Take 1 dollar and divide by 0.043)

Given a cost of $6.6 billion in 1860 dollars multiplied by $23.25 value, the 2006 cost of the Civil War equals: $139.5 billion.

Going by these figures ($6.6 billion for the Civil War 1860 and $2 trillion for the Iraq War in 2006), the American Civil War cost 1/14 the pricetag of the second Iraq War.