your assumptions may be correct - or not, both of us (I guess) don´t work in that business and therefore we don´t know the detailed processes needed and their related costs. In my daily business as a consultant it happens quite often that we look at processes in every detail. Quite often we are surprised about the real costs and where they are coming from.
I think transparency is a good start and not common in the luxury industry. Also whenever I got a quote from Patek it seemed to be reasonable, compared to what others in the same industry ask for.
Example: Even when I just ask for the change of a battery for a quartz movement, it should be different if I ask at an "ordinary" department store or at a serious jeweller. The service and how it is executed should be different and so will the price. Also I expect that the staff will be paid different, for a good reason. But also I have to say whenever I asked for a battery in a department store I had a bad experience (most of the time) and had to pay. At my (trusty) AD I get good quality service, a drink for free and quite often I don´t have to pay for the battery. Just happened (again) yesterday when I needed a new battery for my alarm clock from a well-known luxury brand. Still I asked them what I owe them and the watchmaker just told me: "Well, you are not here for the first time ...
"
Still both of us don´t know the detailed processes, but can (hopefully) appreciate good things in life 
Best,
Oliver