I make quilts for foster kids in my county. Most are 43" x 68" and use my own fabrics for the tops and buy 108" wide backing fabric from Hobby Lobby @ 11.99 per yard. If I buy 2 yards I can get two backing out of it and some left over.
I make mostly scrappy quilts as I don't know what colors they like. I make scrappy quilts for myself also. Since I am using up a lot of my stash they work out best. I buy everything for the quilts myself and use the same as I would/do for my own.
Since this is all the donations I give I don't worry about the cost. Last year I made and gave 33 quilts. I try to make as many as I can.