My theory is charge whatever you would have to pay if you went to the store to buy it. I also charge 7.50/yard. Even though you are only going to use half the cut, I charge the whole amount. You are never really sure if you are going to have a project to use the left over cut portion. Right now, JoAnn's has a Baby quilt size packaged batting for $7.50, so that is another comparison price.