$0 because I clean it myself.
Was told not to oil the Janome 6600, so I don't.
My tech did show me where to oil in case I ever had the need to (his shop is almost 150 miles from me).
If you clean your machine after each project and especially the bobbin area, change the needle for each project or hours used, and your machine is not giving you any trouble, why have it serviced?
That said, get quotes in writting up front. Compare if able to other techs. Sounds pretty high what you paid.