Project cost: $28.9 billion
FY 2013 estimate: $1.2 billion
The military's most iconic aircraft is today one of its costliest, with the Defense Department estimating a $2.9-billion tab for fiscal years 2012 and 2013. The 11-ton helicopter, made by Sikorsky Aircraft Corp., is used for air assault, medical evacuation and VIP transport. Two modified Black Hawks transported Navy SEALs in the 2011 raid that killed Osama bin Laden. The chopper's widespread use might not be the only reason the Black Hawk makes the list: Sikorsky made excess profit in 2011, when it sold to the Army Black Hawk parts it had bought from the Pentagon at a lower price. The company charged $2,510.06 apiece for six Black Hawk seat assemblies it had bought from the Pentagon's Defense Logistics Agency for $143.26 each -- a mark-up of 1,652 percent.