To answer some of the questions posed to me, especially John's, I understand that the US (Navair) wanted so many changes to the initial specification of the US101 presidential aircraft that the cost just rocketed. My favorite examples, 'the airstair door opening is too low, we don't want the president to have to stoop as he exits the aircraft, we want a higher door' (not a cheap and easy job to modify the aircraft structure to accomodate a bigger door), 'the downwash from the rotors is too powerful and could damage the turf of the White House Lawn, we want you to redesign the rotor blades (again not cheap and easy and would have resulted in longer blades necessitating a lengthening of the tail boom). Multiply these and 100's more minor mods and I think that you might get the idea.
Jack, no one is blameless in this game, but even to start with the customer's performance requirements/spec are pushing the bounderies of the available aircraft (from all the manufacturers), especially naval/ASW aircraft full of fancy 'stuff'. Then when they start asking for changes when you thought that they were happy the original aircraft spec then things get difficult, especially the weight.
I guess it's a bit like agreeing a price on a new standard model car and shaking hands on it, for the customer to say just before he takes delivery that actually he wants built in Sat. Nav./GPS, metallic paint and alloys wheels.
Henry Ford had the right idea, any colour (color) as long as it's black.