I always hate to make comment on labor prices. What I can say about that job is that in our shop we leave it to a couple guys who have done it before.
Its a job that experience plays a big part. Technique really matters to results. I don't remember how much time it takes as our best guys probably do it in less than 1.5 hours. I would guess that the book pays 2-3 hours and parts are inexpensive although we find a surprising amount of belt tentioner/bearing bracket problems when these are apart.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician