I was about to open a new thread. Guess it is better to mention here as the thread is not old yet.
From Feudal archer archer to FU Castle Age xbow costs 2175 resources (550 wood, 1025 food, 600 gold). This is excluding University which costs 200 wood.
FU Knight costs 1440 resources (1070 food, 370 gold).
To make this simpler 21 FU knights = 30 Xbow in terms of resource. Practically it will be 35-40 Xbow as food is more valuable and hard to come. And obviously Archer player have the advantage of massing them from Feudal.
While Xbow+Bodkin is a very big power spike, I think the two late castle techs (TR and Ballistic) are a bit expensive than what they provide. I honestly think Xbow upgrade can be even more expensive, +25/f/+25g. But TR and maybe even Ballistic can be cheaper by 150 resources total in return.
In Imperial Age FU Arbalester cost another 2350 resources. From Feudal it will be 4525 resources (550 wood, 2325 food, 1650 gold) in total.
FU Cavalier costs another 1650 resources. That’s 3090 resources (1995 food, 1095 gold) in total.
So 47 FU Arbalester = 35 FU Cavalier. I think against generic Cavalier, Arbalester is okay. Cavalier with bonuses and Paladin are most of the time still feel OP. But for this case, I guess nerfing those civs individually will be better.