Years ago -- too many for me to remember exactly (sigh!) -- the price of handmade items was figured by multiplying the cost of materials by three. Even if you were able to find a charm pack, and it wouldn't make a very large quilt, would it, for around $9.00, the cost of the quilt would start at $27.00. Then figure in another charm pack or two to make the quilt a really usable size, add the cost of the backing and the batting, and you have a truer idea of what a quilt would be worth.
$20.00 for a quilt, unless it had been made for a doll bed or something that size, would be kind of an insult, wouldn't it?