Stationing American forces overseas has not always been as large a financial burden on the United States that it appeared to be. As the economies in West Germany and Japan recovered after World War II, they reached a point where the United States demanded, and got, payments from those countries to cover part of the expense of keeping American troops there. Since then, Japan and Germany have paid over a hundred billion dollars in such payments, and since 1991, even South Korea has made similar payments. South Koreas payments are now $661 million a year, but are being cut 8.9 percent to reflect the withdrawal of some American troops. 

While the cost of maintaining troops overseas is high, its not as high as stated. The American troops would be paid and maintained wherever they were, and duty in Europe was always seen as a recruiting tool. The tours there were three years, and you could bring you family. Perhaps the biggest loss to American taxpayers was that American troops overseas spent most of their pay overseas. This cost lots of American jobs, and a vibrant example of that can be seen when American units are sent to Iraq for a year, and the businesses around their U.S. bases suffer economically for as long as the troops are away. Fortunately, the troops in Iraq cant do much shopping, and spend most of their pay when they get home. 

But for most American troops overseas, the main additional cost is travel. The troops are moved economically, usually on chartered aircraft. Theres also the additional expense of shipping ammunition and new equipment. Although in places like Europe and East Asia, a lot of equipment can be purchased locally.

Its an accounting nightmare calculating what the exact additional cost of having troops overseas is. But in the long run, it isnt as high as the numbers thrown around in the media. Iraq may even decide that its in its best interest to have some American troops permanently stationed there (for protection from their ancient enemy, Iran). In that case, oil rich Iraq will be under some pressure to pick up part of the tab. In the case of South Korea, all the money they contributed went to pay South Koreans working on American bases, and for supplies bought locally. The South Koreans wanted the American troops to stay, to aid in protecting them from North Korean aggression. Its a form of peacekeeping that American troops overseas dont get enough credit for.