High Elf confederation leaves me super poor on Vortex campaign? I'm trying to power through my first campaign. I'm on turn 50, I've got a pretty healthy economy going. I've confederated 2 of the High Elves into my army and I'm very friendly with the others but now if I confedate a 3rd army (I've tried all the other High Elves and this happens to all of them) my gold per turn goes from being 5000ish on green to 3000 in red.

I'm assuming it's because I losing out on trade but all the guides I look at all say confedate all the High Elves ASAP.