As for what they charge....
It depends on your area, and what you want to have done. Some markets charge by the square inch, others by the square foot or yard. The more dense the quilting, and/or the more specific to your quilt top (custom), the more per square inch.
For example, an allover meander would cost a lot less than drop-dead gorgeous heirloom quilting. There is a large range between those two. Not every quilt needs heirloom quilting, and it's a shame to do a meander on a quilt covered with needle-turned applique.
Once you find a quilter, work with her. Between the two of you, you'll find just the right balance of what your quilts needs and your checkbook.
HTH!