I would have to agree with Ground Girl on this one. People bring their car in to an Authorised dealer for maintenance and dont even bat an eyelid at paying labour rates of £70 plus (over £100 per hour for premium brands) and yet in aviation where the safety and quality of workmanship has to reach a far higher standard (in most cases!!) we complain constantly.
My understanding of the spares differential between the automotive and aviaition sectors is that you pay for individual quality control and not batch testing as each part has to be tracked.
My advice would be to know what your paying for (i.e. limit as much as possible the opportunities for hidden extra charges) and approve everything!!