Originally Posted by Weasel

It isn't common for a control arm to cause a squeak in the rear axle, but I wouldn't count it out... I'm guessing the tech(s) narrowed it down to there via actual diagnosis (or at least hope), but if the problem is in the non-greasable ball joint of the arm, you could try getting a grease needle from the parts store and inject some in there to see if it helps before spending the $450.