As others have mentioned, it's baffling that Ford does not offer an upgrade from the factory. I had the opportunity to drive a Camaro with the NPP option the other day and it sounded great from inside the cabin and got decently loud when you got on it.
the way
It's a good thing to think about. As everyone knows, cars are depreciating assets. Buying a new one in most cases is not a "smart" financial decision - but do it because we love them. Not everyone understands spending a chunk of dough that loses a bunch of value the second you drive off...
One thing that confuses me is that the Machined Foundry low gloss wheels are so much. As the GT premium already comes with 18 inch rims, who would pay 1100 for these? Don't get me wrong, I like them (and actually want them) but I don't get the huge price. Ford.com has them for an extra 155 bucks...