As a former textile restorer I have to agree with ckcowl. I would add - give a written estimate and make sure that they are aware that if they don't pay they don't get their quilt back. Sounds very hard, I know. Luckily I was never "stiffed" by a customer but I have friends who were out £100s. And keep in mind that if you have underestimated, that you were adding to your skills and doing something that you love.