Just Wondering

I purchased these flannel sheets from ShopNBC on sale, it's good quality 5.6 ounce flannel and it was on clearance for about $30.00 and then the shipping was $10.00, so total around $40.00.  I know that many don't like to use sheets for backs and none of us like to pay shipping, but I figure if the price is low enough it is still a good deal.  I started wondering how much fabric I actually get from a set of king sized sheets.  This flannel has been washed, so it has shrunk already and I ended up with 2 pieces 13.5 by 72, and 2 pieces 36 by 40.  I also have 1 piece 100 by 100 and another 68 x 104 inches.  All of my measurements were under rather than over and I figured about 21,896 inches.  Since a yard has 1296 inches, I figure that I got 16.9 yards from my set of sheets.  That comes to about $2.37 a yard, which isn't bad at all and I have mostly nice big pieces to start off my back.  All in all, I'm happy with what I feel was a bargain.  If only I could figure out some good use for that brand new elastic.  
PS  Another thought.  This is for the back of a quilt for my bed, but if it were for a gift, or if I liked to sleep on flannel (which I don't, but I live in Florida), I could not cut up the pillow cases (the 2 pieces 36 by 40 inches) and give them to the recipient of a gift.  I know some ladies make pillowcases as gift wrapping.