I've sold several quilts, but the majority have been art quilts, basically for the wall. The base price is set at $90.00 a square foot and adjusted from there depending upon technique and surface design or embellishment. Quilt tops, that are not quilted, I've figured out how much in cost the fabric was and was grateful to break even. Time was not factored in since they weren't commissioned tops, just house cleaning and getting rid of extra tops I knew I would never get around to quilting. If the top is quilted and you did the quilting, factor in the time costs for your region. If you paid for the quilting, of course add that to your yardage costs, batting, thread and tax percentage, and something for your time. If the price is too low, any future commissions will have you fustrated at working so hard for so little. Reverse psychology, you will be better respected as a craftsman if you don't de-value your work.