I'm sure this is a stupid question, but based on the descriptions, I don't see why not! Was curious if I could pop out -40% Power Word: Pain cost or not :x
I would like to note that you CANNOT stack several glyphs of the same type to increase the effect. Upon attempting to inscribe a duplicate Glyph at the Lexicon of Power you recieve the message:
"That Glyph is already inscribed in your spellbook."