I have only made T shirt quilts for others and I charge basically 6 cents a square inch plus any materials like batting stablilizers and backing that I supply. That would be for simple squares. The smaller the pieces I have to work with the price goes up. The more piecing I have to do the higher the price. It is a matter of time spent in labor. Don't forget you will have to process all of the shirts, launder, iron and then cut up etc.