Early in this one game i had 5 military units and 3 workers. My unit maintenance was 11g per turn. So i thought 1g per military and 2g per civilian unit. Then i saw this bit about supply in the military overview. What does that mean and how does it affect unit maintenance?
The supply limit based on your empire size is not related to the upkeep cost. Instead, if you exceed the supply limit, all your cities take a 10% production penalty. In most games, you will run out of money before you get to that point.
Workers cost 9-11 gold for a pair. If you liberate (delete) one, you get no benefit. Liberate the second, and you'll get the 9-11Gold reduced from your maintenance costs.
Military seems to work the same, but I'm sure that it's not every pair. Riflemen come in a quartet (retire 3, no benefit. Retire the 4th, 9-11 gold).
I wasn't watching too closely, but I believe Barbarian Brutes cost 6G each (they may have been paired, I can't remember...).
Also, I don't know if death during combat counts towards the unit maintenance reduction.