» Fri Oct 19, 2012 6:06 pm
I'm pretty sure your raw skill (in this case, Conjuration) also plays a role in how much magicka is required to cast a spell (in addition to the appropriate spell-level perk).
On my current PC, I haven't perked Conjuration at all, but I've been training it the last few levels (via a trainer) and the MP cost of the spells drops each time.