Benefits of the Iraq war

So I'm sure people would love to know what benefits we've made after 5 years of war and
billions of dollars spent on the war have gained us. According to NCPA.org, "When postwar oil markets stabilize, the price of oil could drop back to around $20 a barrel -- saving the U.S. economy $55 billion to $60 billion a year." Once gas prices are down to 20$ a barrel, the world's oil reserves will be depleted quicker, thus economists fail to take this into accord. The principle of supply and demand can only work if there is a certain supply, if everyone is buying oil at 20$ a barrel, then more will be sold and thus less will be in the ground. On the upside, economies all over the world as well as in the US will be strengthened by cheaper oil, why? because in many foreign countries the people pay an arm and a leg just to fill up a tank.