I got mine I think for $320 shipped ... installation requires the removal of the door panels and not much else.
Keep in mind if you're searching that there are several variations ... some with BZA some without, some are the first version with the dotted arrows and some the newer with the linear arrows.
I think it makes a huge difference on the Denali which really should come stock with them.
No kidding. You would think a $60k truck would come with upgraded mirrors! Even the Tahoes have chrome top halfs. For $320, I'd rather keep mine. I'd rather spend that money on a CAI or put it towards audio equipment. The mirrors aren't a big deal to me. My list of mods is long and moving along slowly so the mirrors will probably be towards the end of the list.
BTW, thanks for the advice on the rear emblems. I think it looks 1,000 times better than stock. I ended up using a GMC chrome emblem b/c my truck is black with chrome parts and the chrome just went better with the truck than red. I'm probably the only person that notices them though. Actually, there is a guy where I buy breakfast that works at the local GMC dealership (I know b/c he wears the company shirt everyday.) I drove by him one day and I noticed him staring at the back of my truck as I passed him. Another day I was walking behind him as I was talking to my truck and I saw him look in my cargo and stare at the back of my truck. Only GMC fanatics would notice them but it's the best mod I've done so far except the BB tune.