I don't recommend doing custom quilts for strangers either. You NEVER get what it is worth and some can be very picky. If you insist on doing the quilt, please make sure the customer chooses and buys ALL fabric, thread, and backing (and pattern if needed). Then charge your $400 for piecing the top. If you are hand quilting it you need to charge by the inch for that. Or let them find a long arm quilter and deal with that separately. Usually after they figure out what is is actually going to cost they will buy one at Walmart and forget the project, which is usually a good plan. I have done several of these and will NEVER do another! I quilt only for family and friends.