Here is a price list from a small shop near us in Claremont, NH. I've used their service and they did a nice job. I really like the people - it's a mother/son team. Remember there are many factors such as experience of the quilters, local economy and so forth. This page is very open about what they do. If you want something special, or hand guided designs, you need to talk to the quilter.
http://fourpinesquilting.com/machine_quilting.php