I charge by the square inch. $0.15 up to $0.20 for edge to edge, $0.25 and up for custom. I don't do heirloom. Batting and thread are extra, batting is priced at retail, and thread is $1 per bobbin for solids and $2 per bobbin for variegated threads.
So for that size quilt, at $0.15 per square inch, the quilting would be $145.80, plus thread and batting.