I have a barely used aFe CAI for the Z4M. I bought it about 1.5 months ago, used less than 1,000 miles, but decided I wanted to keep the car stock and put the money towards some cosmetics. (Hello Mstache).
The only signs of wear is on the bottom of the metal housing where it was scraped during installation and moving it around. You can't see it once installed, it scrapped against the bolt sticking up for the rubber bumper. Other than that it's got some finger prints on it.
Other than that, it's like new.
$350 New England pick-up / ~ $365 shipped (can get exact shipping quote)