Like, how would you readjust the cost of all your units if every unit had anti-air ability? Or how about giving +1 attack or defense to any unit? I know it's pretty map-specific, but just wondering if there's a way to determine cost differences between units as correctly as possible.

I like unit costs being as close to each other as possible. Like decreasing air units' cost as much as possible while not making them overpowered. Or something.