I used to make quilts to sell and it was still fun. Just figure how much time it takes you to make the quilt. For instance, how long does it take to make a block TIMES how many blocks are in the quilt. Don't forget your time to get the fabric, washing, pressing, cutting, etc. Add 20% for all those things you forgot.
Now, how much do you want to make per hour? Are you happy making $1 an hour, I know I am not. However, I don't need to make as much as someone going out to a job, as I don't have the expenses of commuting, work clothes, etc.
I would never do it for twice the materials costs. I tend to buy things on sale. When you get a job done by a plumber, carpenter, or auto mechanic, you are paying twice what they paid for materials and THEN they add in their labor costs.
PS - if they don't want to pay the price you come up with, smile sweetly and say, "Try Kmart, I'm sure you'll find something you like there..."
PPS (not really, that's kind of snarky. But you can think it.)