Funny, I have a 'regular' Tahoe air deflector headed my way. I wanted to get a deeper one on the truck to hopefully gain some mileage. We put a Suburban/Tahoe air deflector on our 2002 GMC 2500HD when it was new, and we gained a solid and repeatable 1 MPG. I figure if we can get that out of the 2018, it will pay for itself soon, given the amount my wife drives.
I, too, am shocked at how much the PPV deflector goes for, but even more shocking is how much the online GM Parts places want just for shipping!!! I found an Amazon seller who claimed to have a regular Tahoe unit for just a bit more then the online parts places show, but without the heinous shipping charge.