There are many who'll say multiply your materials by two or three times to come up with a selling price . . .but if your materials were only $10 . . .would a pieced quilt you spent 3 weeks working on really only be worth $30 max???
I keep track of my time in hours . . .decide what I'm worth per hour and charge accordingly. It breaks my heart to see beautiful pieced quilts that have 160 or more hours put in . . .selling for $125. That's less than a $1 an hour! It's up to us to price our work for what it's worth . . .it IS afterall, art. There's a demand for that art. Pricing correctly keeps the market fair for all.