"I have always been a patron of the arts which has only increased with Balthazar in my home." Dean gets a quiet laugh from the angel because Balthazar had, on occasion, pulled out things that he didn't understand. That road was two way too and the other angel just as confused.

"Everything?" Lucifer comments off hand. "The honest answer is my presence is now attached to the creation in which you exist and you are the first human I have met from the realm of my partner. The perspective you have may be valuable."

It is the honest answer and something Dean will have to adjust to. This Lucifer does not lie or manipulate truth as so many others do, as he assumes the one in Balthazar's creation would.