I was wondering about these costs being bandied about. I found an article at http://www.globalsecurity.org/military/systems/aircraft/kc-767.htm
which is informative. It says, among other things,
According to a December 2001 Office of Management and Budget (OMB) estimate, the lease plan would cost $26 billion, nearly three times the cost of simply purchasing the planes.
A big chunk of cost here is due to leasing rather than buying. Congress is allergic to appropriating current money, if they can put of the problem for later, when another Congresscritter may be in office anyway. Boeing would rather just sell the planes as military tankers.
More cost inflation cited in the article:
This leasing program also will require between $600 million and $1.2 billion in military construction funding to build new hangars, since existing hangars are too small for the new 767 aircraft. The government would also pay another $30 million to $60 million per aircraft on the front end to convert these aircraft from commercial configurations to military; and at the end of the lease, the government will to pay for $30 million more, to convert the aircraft back.
Some of the cost is due to construction, and is not going to Boeing. More is due to the insane idea of building commercial planes, converting them to tankers, and reconverting them to commercial airliners later, another absurdity of the whole leasing idea.
If the government decides to lease 330s instead of 767s, all these cost inflators will still be there.