Alternator noise

[double06]

Well, I went by a shop today to have someone listen to the X. I was hoping that he would confirm my suspicion of a pulley bearing going south. The noise is coming from the diver's side of the engine and he stuck his head in and almost immediately said it was the alternator. Apparently you just can't replace its pulley and I'd have to buy a whole new one. I figured it wouldn't be that bad as I know generally what alternators cost. Well, I got the 05 4.4 so its water cooled! Ouch, he quoted me a BMW OEM for 500 something. WOW!! So my question to the masses, does this sound about right for an alternator to make that noise? All lights are fine and I'm getting no warnings etc, just a whine from the alternator. Also, where can I get a better deal on a new one? On a side note, he told me labor for it would only be about 120 so If I can find one he will put it on.

Thanks in advance