"The US is spending about $10 billion a month on Iraq and Afghanistan. By the end of this year, the total funds appropriated will be nearly $600 billion – approaching the amount spent on the Vietnam or Korean wars, when adjusted for inflation.
However, the actual impact of the war on the economy is different than in the past, largely because the US economy is so much bigger now. During World War II, some analysts calculate that the US spent as much as 30 percent of its gross domestic product (GDP) on the war effort. The Korean War, at its spending peak in 1953, represented 14 percent of GDP; Vietnam was about 9 percent. The current war, however, is less than 1 percent of America's annual $13 trillion GDP."