[Cainehill]

In addition to what Graeme mentioned, there are summoned units that you'd have to experiment via trial and error to determine the upkeep for, since they have no purchase price.

This can be problematical - if you're running out of gold to pay your troops, summoned troops are usually the way to go, since most don't cost upkeep, while others do, and the documentation for the spells doesn't mention which cost ongoing upkeep.

Similarly - most summonses don't require food. Others do. Regular trolls don't eat (and I think, don't cost upkeep) while sea trolls require both, for example.