In a notable addendum to this post:
I noticed a couple weeks back that the cost for Elixir of Major Firepower has, in fact, been reduced! Much rejoicing ensued. Relative to the cost in mats for Major Frost Power, the Firepower equivalent now also costs 2 motes of fire, rather than the original 3 motes per elixir.
Yay! I never saw any documentation of this change, but hey, I'm not complaining. :D