Editing Yagura:SRD:Spellcasting Strain (section)

=====Empower Spell=====
Empower Spell only carries a metamagic cost of 1 spell level, not 2. 

The reasons behind this are fairly straightforward. Casting an empowered spell of level X has an effect roughly equal to casting a spell of level X and a spell of level X-1. Since we know that the cost of casting those two spells is the same as the cost of casting a spell of level X+1, we charge the same amount for this metamagic effect.