God and Creation more Valuable than God?

Perfect Being Theology (PBT) holds that God is the most valuable being.  Either creation is valuable or it is not.  If it is, then it seems that God+creation is more valuable than just God alone.  If creation isn’t valuable, then it seems odd to motivate God to create--this, on top of the seemingly overwhelming evidence that creation *is* valuable.  What’s the solution?

Thomas Morris holds that we should just think that PBT asserts that God is the most valuable *being*, and that God+creation is not a being, but a sum of beings.  So God is not the greatest sum of things, though he is the greatest being. 

A better route, I think, is to hold that creation has its value extrinsically.  Nothing created is intrinsically valuable.  This seems to mesh well with the intuition behind St. Thomas’s “participation” doctrine.  Mark Murphy defends this view well.  

In Murphy’s words: “This is what goodness by participation is like. If one being is intrinsically good and another is good simply because it participates in the intrinsic good’s goodness, there is an additional good (and even agent-neutrally good) thing, but there is no more goodness than if the intrinsically good thing alone existed.”