the price you can charge is really going to vary based on your location in the country, the other quilters/artists in your area, and the type of work you do utility quilts/art quilts.
i live in Metro NY and i charge $50-$100 per square foot depending on the extent of the work that went into the quilt.
i only do art quilts and the utility quilter is not my competition. people who buy my work are art collectors and my competition are other artists (paint/sculpture/etc).
i started out doing shows and competitions to develop my name, product, and client base.
now i do 1 or 2 shows a year and most of my work is done by commission only.
depending on the size of the projects i can take anywhere from 3-6 projects a quarter.
i have a cut off for project that are due in december of june to insure i can meet the deadline date.