Some concessions must be made in the area of cost and maintenance to balance an entire unit list for the faction. Cost, maintenance, and build times are the ONLY factors we have to play with to try and make sure that both the AI and the player have incentive to create a balanced mix of armies. We can't try solely to be realistic in terms of the relative cost and maintenance of individual units, as then little incentive would be present to build some units, and little incentive to build anything else for others.

Thank you for your suggestion!