I'll stock up on bargain fabric that I'll use for backing. About a year (more..?) ago Quilt in a Day had a sale where you bought 10 yards for $25 in a certain color way. So I bought a bunch of those, and the pretty ones go onto quilt tops and the not-as-pretty ones get pieced to become backs.
It's difficult to pay $25-30 for backing fabric when I could spend that for another quilt top