first off, I would tell him what a king sized rag quilt will WEIGH and that he would have to always take to the laundry mat to wash/dry it!
my friend in AK did one with just flannel top and bottom and and thinsulate batting, 110" sq...Wet it weighed in at 38 pounds! Dry it was over 25!
PS, the value of anything is simply what someone is willing to pay you for it!