I know that it's heavy armor! No, it increases the cost. It didn't do this. This ***! It makes it useless. Sirorias doesn't increase the cost bc it increases the damage. Why should it for Elf-bane. Another STUPID ZOS decision in my opinion.
You know what, I want my alliance points and gold Matt's back!
If elf bane increases the cost, that would be a bug. The only thing it's supposed to do is increase some durations. You may want to do some investigations into why you're seeing a cost increase that nobody else seems to be seeing. Get some screenshots and post here with before and after setups if possible.
I went back and tried to unequip and re-equip but it isn't doing it anymore. Maybe I'd been parsing to long or the buffs from the iron atro ran out as I was changing gear.
Forgive me everyone, it seems I'm chicken little on this one. I apologize and hope you can all forgive my mistake. Didn't mean to waste anyone's time.
Elf Bane doesn't actually increase the cost, but light armor has a cost reduction that you are losing by switching because it's heavy. Keep in mind that heavy armor has passives for heavy attacks restoring 25% more resources, so they kind of balance out. I run a lot of mag builds in heavy armor so you can do two damage sets with the resistances of heavy. It's just personal preference.