I've never understood the 3 x cost factor for quilting, because that would mean you would get paid less if you work with fabrics that are cheap or on sale. I can see where it might make sense in an industry where costs are pretty much the same, but not for quilting. But be sure, as others said, to get the amount agreed before you start. Non-quilters seldom have any idea how much time it takes to make a quilt, how much fabric and batting it takes, or how expensive those materials are.