Its not the camber that wears the rear tyres out, its the toe in. The rear toes in towards the center of the car, which in-turn scrubs the inside of the tyres out.
Sorry to disagree, but it's camber and toe out, that ruins the inside edge...More so the camber, as you are putting more weight on the inside edge of the tyre, which in turn causes the tyre to wear in that area quicker.(have a look at the tyre angle, next time you can, with this style of rear end set up, to understand what I am referring to)
They also call it toe out, because the the tyre is pointing outwards, where as toe in means the tyre is pointing inwards, when you are looking at it, from the front of the car. Again, means that what ever edge has the more weight on it, during straight travel, is the edge that will wear quicker.....
A 4 point aftermarket camber kit allows camber and toe to be adjusted.....Only issue that arises is, when you put more weight into the boot after it has been set.....it tends to lower the car, therefore changing camber and toe settings.
Finally...$650 sounds about right for one fitted, with a 4 wheel alignment done.....
