[Sombre]

If it were tied to population it still wouldn't be worth paying the extra time and money for the high admin city. Forts are to make more commanders (mages) per turn and to get some more resources worth of troops a turn nearer the front lines, with defence and income/supply increase coming as largely incidental concerns.

I'm currently thinking all forts should cost roughly the same, time and money both. It's less confusing for the player and it's easier to identify when you're actually getting a good deal, plus it rewards the nations with 'better' fort types. When it comes to nations like ctis and their swamp buildable, you could just make that particular type, swamp city for example, slightly cheaper/faster. You'd do the same for other special fort types. So say all forts would be 1k at 4 turns, with specials being 750 at 3 turns.