Not worth it at all. Would have been worth it if we hadn't been lied to about WMD's in Iraq.
Afghanistan is not worth it. It brought the Soviets to there knees, will do the same to us. If there truly is an imminent terrorist threat in Afghanistan, the CIA, with their black budget, has more than enough resources to fight a covert war to take out al queda in that region. Oh, wait, al queda is a CIA creation from back in the 80s.