Let's see what their reply is.
I have not heard that service costs are so much more costly than other watchmakers. However, I am aware how much many other makers charge for service. I've paid $750 for a simple AP jumbo service without any refinishing up to $10000 for servicing a repeated or sonnerie.
Most independents, in my experience are very accommodating when it comes to servicing one of their watches. These makers do not make many watches and are fairly amenable to keeping their customer base happy.
Vianney in particular is most definitely his own man. He beats to his own drummer and, his time is valuable. I hear Vianney has waiting lists for his Trio and Antiqua. Vianney makes basically the entire watch in house - case, crown, dials, hands, only the movement plate and escapement and mainspring are outsourced and finished in house. Taking his time away from his normal activities obviously comes at a cost.
Regarding your question about can anyone 'good' work on a vianney watch - sure. I have seen watchmakers work on some crazy claret base repeaters and sonneries, nutty gentas, mullers, etc. He'll, parmigiani, Voutilainen, even Daniels got started by working on restoring old watches. While the antiqua is complicated, I'm sure it's one thing to invent the movement and another to service it.
We have had the discussion before on these fora - servicing issues in this day and age are 'normally' and 'usually' easily taken care of. Price paid for service is a relative discussion. If that's what your issue is, what is a fair service price to pay for a watch costing 1000, 10000, 50000, 100000, 150,000?
Service is a personal choice. I have some watches which I service every 3 to 5 years and others over 10 which have never given me an issue (eta 7750 based). Some pieces I polish - others I dont. Again - it's personal.
I will let you know what I hear from Janvier SA.

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No worry my friend! Service schmervis! You know lots of folks to help get anything done!!
Best,
asg