The only Collector's Edition that I have bought in years was the SC2 one, and I just bought that because gamestop had some silly preorder + coupon code + beta key (which I sold to a friend) and overall that put me under the cost of the regular edition.
But other than that I've only bought collector's editions for profits, ie every WoW expansion buy a couple of collector's editions, hold for a few months turn around for double or triple the cost (and before someone jumps on my back, it is the main way I fund my gaming habit, it's not like I'm making boatloads of money, all of it gets cycled back into games.)
To be honest, most of it isn't really worth it, a lot of them are just plastic junk, and things like the music, odds are you'll find it on iTunes for cheap, and extra footage and behind the scenes, you end up watching once and never again.
You see things like a kid making functioning assassin blades for like $20 from his local hardware store, you'd think someone like Ubisoft (or whoever owns Assassin's Creed) would go hey, we could make the same thing for pennies and just add a fake plastic blade, this would sell for tons of money, and thus make something actually worth buying.