Cost of servicing probably is no more than 30-40 years ago relative to the initial purchase price of the watch. As discussed today in 1970 you could buy an rolex air-king for approx £120 - service costs - £14 - so about 10% of value of watch - ratio is pretty much the same today.
I think 'Mechanicals' have a long term future as luxury items. Like they are today. IMHO