I have found this article to be very helpful:
http://www.bryerpatch.com/faq/marketing.htm
I've only been commissioned to make one quilt, and even though my customer said she'd pay me, I didn't make any money on the deal. By the time she reimbursed me for fabric, backing, batting, and the extra embroidery she decided she wanted AFTER we had discussed price, we were at a price that I think she felt was pretty high. Since she was a friend, I decided to let it go, but I'm much wiser now.
I've used the above link to determine how much my quilts would cost to replace, then advised the quilt recipient to insure it for that amount. They have the choice of insuring it or not, but it subtly makes the point that they should take care of that quilt and not use it as a dog bed or car cover. Ha.