For the price of the Iraq War, we could've trapped Osama Bin Laden in Afghanistan by surrounding the country with a 100-foot wall made entirely of hundred-dollar bills.
Afghanistan's borders are 5529 kilometers long. Since a hundred dollar bill (like all of today's paper money) is 156 mm long, it would take 35.4 million of them to surround Afghanistan. Since a hundred dollar bill is 2.61 inches tall, it would take 460 of them to make the wall 100 feet tall. This means it would take 16.3 billion bills to create a 100-foot wall around Afghanistan. Given the face value of each bill, surrounding Afghanistan and Osama in a giant wall of Benjamins would cost $1.63 trillion, which is less than Joseph Stiglitz and Linda Bilmes' estimate of $3 trillion for the cost of the Iraq War.