I've sold a few quilts, and honestly I undercharged for one of them. It was a huge king size, 120x120 center with an 8 inch border. I got $1000 for it, but it was hand quilted. Blinking thing took ages to hand quilt.
One of my co-workers saw me piecing my GFG quilt top (actually just one of the flowers) and asked me to make her one like that. I said I would at $1 a hexagon, plus $250. She decided against it.