My Grandmother charged $100 per quilt 40 and 50 years ago and most of them were pieced with scraps and stiched in the ditch only. Time is worth so much, but enjoying your work is important as well. If you decide not to do the job, you may consider offering to help her make them herself. Don't do if for $300 if it is just for the money- Do it because you want to do it.