Should be that (actual formula is cities * techs * tech-cost / <number>, as tech cost is fixed its basicaly cities * techs * factor) , but it somehow seems to be a bit bigger than I calculated/anticiapted. Tech cost is also adjusted by server setting a bit. Maybe I somehow miscalculated interaction with that. Still for me upkeep does not seem too tragical:) And when someone builds great library it should become much better, at least for those that have libraries... And I am way too slow to that.
Well I have never used that feature:). But someone asked so I answered. Sometimes cities can produce multiple units per turn, though this is more for end game as far as I understand, say city has 100 prod, and is building unit that needs 40 shields. If it has two build slots, it should make two of them. At least as far as I understand.