The $770 million number is rubbish. Australian policy when buying aircraft is to include the initial cost of the plane plus the training and support costs over the next 10 years. The initial cost of the plane is usually 1/4 of the total outlay. When we bought the 24 Super Hornets we paid A$6 billion (US$4.6 billion at the time) which equated to $250 million per aircraft for 10 years. This calculation was possible as the cost and training of the Super Hornet was a known entity by the USN. The F-35 won't be operational until 2018 so nobody has a clue what its training and support costs will be and hence the $770 million figure is pure fantasy.
