I own a 05 QP. I have done three services at this time and one clutch replacement, as well as one full set of tires have been changed. I now have 19000 miles on the car. Yes, the service expenses are more than you would have with a Mercedes, BMW, Porsche or another high-end, high-volume manufacturer. The cost is less though than at Ferrari, Lamborghini, or another one of those super-high-end marques. I only have mine serviced at factory authorized service facilities, as there always is the one or two warranty issues they need to fix. Overall I did not have the car in for unscheduled issues and the car proved exceptionally reliable. Mind you I have put the 19000 miles on the car in the course of a little over 1.5 years. Service Tech thinks I have no problem with the car because it does get used a lot. Maseratis are high performance cars meant to be driven, not kept in the garage.
Anyway, my expenses were:
1. 6,500 mile service (oil change, lube job, general service items, including material and labor) $ 745.00
2. 12,500 mile service (lube, oil and filter change, general service items, plus CHANGE OF CLUTCH, CHANGE ALL TIRES) $ 9,800
3. 18000 mile service (first "big" service, changing all fluids, filters, ...) $ 2,700
So, all in all not too shocking, but more than you would pay with any other German or Domestic luxury brand. I am excited and elated that my QP has a perfect service record though and is always ready to go!
Hope this helps you!