You will need between 9-10 yards of fabric for your 12 1/2" blocks to make a quilt 72x72. When I charge for a quilt, I charge 2.5 to 3x the cost of my materials. Based on this and the amount of fabric you'll need, $150 - $200 doesn't sound too far off of what it would come out to. Also, you may not be quilting it with batting, but you have to put the "x" in all the squares and also cut all that fringe. After that, you will have to wash and dry it a couple of times to make it rag properly before you can give it to the customer. This will take time, not to mention the use of your washer and dryer and the mess it can/will make. Just my opinion, but keep all the steps in mind when figuring out your price.