I made my hairdresser a quilt for her wedding (still have to bind the dumb thing) and she just moved into a new house...so she asked me if I could make 2 reversible twin-sized quilt for her daughters. She didn't want any piecing, just two different colors on the quilts. I told her it would be much cheaper for her to buy quilts at Walmart! I quoted her $300.00 each quilt...the quilting alone would either be whole-cloth type or BORING large crosshatching. She decided Walmart would be fine.
When I do commissioned quilts, I have found the fair price to me is at least 4 times the cost of all the materials, including batting. So quote your cousin a high price for making the quilts - if she has the nerve to ask you to make them (probably expecting it to be free to her), then you have to have the nerve to place a high price on your creative talents and time!!!