As TMedina said, it's the contracts. Having worked on government bids before, I have tp tell you the process is a little arcane. In many contracts, if you are selling Model T, you have to agree to make Model Ts for X years, and to continue to have parts available for Y years after the end of the contract. In the case of the G2 and the 6P, more than likely the contracts are open ended, unlimited quantity quantity ones. Usually a contract will state that any significant change in specifications, even if supplied at no additional cost, will require that the product be opened for re-bid, with the possibility of losing the business to a competitor. Also, after this length of time, all of the production equipment and R & D costs will have depreciated out, greatly improving the profit margin. For those of us old enough to remember the Chrysler K-cars, that is what happened there. With the tooling and R & D costs depreciated to zero, Chrysler was able to drop the consumer price several hundred dollars, and still keep some increased profits for themselves.(It is amazing how useful that one Business Accounting class has been over all these years, even if I was an IT wonk!)