Acme starts production but runs into alot of problems which cost more money. Timeline is ignored as are penalties in order to get this "badly needed" tank into production. First prototype rolls off the assembly line but fails to meet quality control standards, more time more money and more overruns. Second prototype comes along 3 years behind schedule. Passes quality control but fails "survivability" tests. More well you know. 5 years later the third comes along and makes it all the way through. However a newer better tank is already in production and only 17 of the "badly needed tanks" are made and never used. The contracto is paid the full price for the production of 50 tanks. General X retires and goes to work for ACME along with several of his superiors.
Don't think this is realistic. Read the Inspector Generals report on the proposal to production of the Bradley Fighting Vehicle. Not quite the same but damn close. It happens all the time and we pay for this ****.