Show me where I ever said it did!
What I HAVE said is that a great many costs (whether or not YOU recognize them as such is irrelevant) imposed on the economy by the current communist inspired income tax system have been identified and, to some extent, quantified and that MOST of those costs would go away with the implementation of the FairTax. I stand by that statement completely!
And the context of the Payne study treats lost growth as a cost. Again, lost growth is not responsible for the current price level of products.