The first thing to decide is whether you want to make the quilt at all, and if not, just say so and be done with it. If you would like to make it, then get a rough estimate of how much the materials would cost, and don't forget batting and thread, and any special tools you need for the quilt. Just telling the person how much the materials will cost will probably be enough to stop the project. But if they persist, then figure out how much you would be happy with as a commission for making the quilt. In some cases, I wouldn't charge anything for my labor, because I would enjoy making the quilt so much and would be honored to be asked. In other cases I would want a hefty sum. I would keep in mind how long it would take to make it, but I wouldn't be comparing it to an hourly wage. Instead I would ask myself "would I be happy with that amount?" Of course I'm retired and I have the time to quilt. This may not be your situation. If you're sending the quilt out to be longarmed then of course that cost is separate, but if you're doing it yourself you honestly can't charge as much as a professional longarmer unless your work is comparable.