Fixed that for you. iPhones are a luxury item. Cellphones are arguably necessary, but nobody's forcing you to drop $400 on a smartphone when there are perfectly free (subsidized) feature phones on every single carrier.
So yeah, I agree with the assumption that iPhone users have a little extra cash to burn.
Edit: Ok, maybe Ferrari wasn't quite a fair comparison, but certainly a car that's a little more than just getting from point A to point B.