When I make a t-shirt quilt on commission I charge $320.00. That includes the backing fabric, batting, stabilizer for shirts, border fabrics and binding. My finished quilts are usually about 65" wide and about 75" long.
I would much rather donate my time to make a charity quilt than work for only $8.00 per hour. As everyone on this board knows, quilting is a skilled art. If quilting was so easy, nobody would need to hire a quilter. Don't sell yourself cheap.