Context on the F-35 Program cost decrease →
Good news: F-35 program decreased by $11.5 billion due to efficiency gains with no reduction in quantities.
GAO: http://www.gao.gov/assets/670/662184.pdf
Bad news: F-35 program is still $107 billion more costly than it was in 2001 and includes 409 fewer aircraft.
GAO: http://www.gao.gov/assets/670/662184.pdf