Its always annoyed me the way it was done in the Essence Companion. On the one hand, Treasure Companion had a very simple system that was applied to Alchemy: The value of a gem is its essence potential (since technically, Lord Research is done by releasing a gem's essence in crafting, the same is transfered over to alchemical base cost). Not only is the linear relation between essence potential and gem value is lost in Essence Companion, but suddenly gems have a different value altogether. I could live with the different essence potential as relate to crystalist casting, but 2 Companions with different value of gems = FAIL.