My LA charges $25 per hour for binding. She will just attach the binding and I can sew it down in back or she will sew the back down. Because she charges by the hour, there is not math problem to work out the number of inches. I think $25 an hour is reasonable for that type of work.
Given that, I LOVE to do binding--I love to make it, sew it on, and hand stitch the back. For me it is such a nice way to finish a project that I have worked on for awhile. Also, as I give all of my quilts away, it is kind of like saying my final goodbye to the quilt.