Every unit in CoN comes in a large group, even officers and missiles. When you produce ASF, you make a large squadron of them (12-24 aircraft or more). It takes 425 manpower for level 1 ASF, and obviously it does not take a crew of 425 people to man and maintain a single fighter. Ships are produced in large groups as well. Do you think a single cruiser could really kill entire tank battalions in hours, or defeat a large naval task force?. Manpower is obvious evidence of this, as well as HP.
Yee Haw