I am with Pickles some of the time. However, last month, our LQS ran a 20% off sale for backing fabric if you brought in your finished quilt top. It was great motivation for me to finish a UFO. She also had some fabric for $5 a yard and then the discount made it really cheap. And it was good quality. I know of another LQS up north that has backing fabric 25% off on the 15th of every month. I suggested that to my LQS. Maybe you could do the same with yours.
judee