I would say if batting and backing are included and the quilt is say queen size, that price actually sounds reasonable. Machine quilting takes a good 5-6 hours depending on the design you pick, plus time to load and unload the quilt. The machine is quite expensive, and certainly takes a lot of training and practice for the machine quilter so their specialized services aren't going to be cheap. If you feel it is too much for you to pay, maybe you could talk to them about a simpler design that could cost a little less? But like I said the price you said seems fair to all the price quotes I have ever seen for machine quilitng.
Rachel