My base rate for my Brother 2003D and Pfaff 7570 was $179.00 the last time I took either in several years ago. I don't take mine in unless there is a problem. I oil where they need it and make sure I take care of the bad needles pronto. I don't know how to time them and parts do wear out so that is when they go see the 'DR.'. The response I received when I asked about the cost of service was that 'you spent $5000.00 on these machines so the service is more complicated', yeah right! I didn't spend anywhere near that on any of my machines!
Good luck on your service hunt!