When a friend's husband asked me to make a quilt (and I didn't want to), I broke down the expenses for him and told him how much time it would take me. I told him the cost of the fabric, the quilting, the batting, the thread, and then told him to decide whether he wanted to spend that much. I didn't hear from him again. First, do you want to do it? If not, say so. If you want to do it, you need to ask a price that you think is fair regardless of what the other person thinks is fair. Then let them decide whether they want to pay your price.