it dosent real make any sense making iron swords. becuse you use 20 time more cola for 1 iron sword then 1 bronze sword. You also have insanly expensive mines and prodciton units. need 4 iron mines for 2 smelters make 1 sword production withe amount of resorucses that takes.
When the unit is only 50% bether it dosent make sense. hade it been 100% bether it might be wourthe it. And well before you reache the 200 limit in armies you can produce the next level.