After acquiring this master level alteration spell, it claims that it's magic cost is ~250 (can't quite remember off the top of my head).
I have over 700 Magicka with all my enchantments equipped.
Using this spell uses ~75% of my Magicka
The math isn't adding up.

Can anyone else confirm?

Man, I thought it was a LOT more than that. Do you have the perk? I thought it costed around 450 w/o the perk and alt at 100. I don't use the spell often so I can't remember. But if you have the perk then ya you're right. Idk what the deal is then.