You could also try your local thrift store. I've bought yardage (about 8 yards) of fabric at one of my local Goodwill stores. & cheap. Of course it is hit or miss w/ choices or if they even have any fabric there.
Fabric.com has some good deals. Not a lot.
Also, on a sewing forum, some folks will purchase bed sheets at thrift shops to use for clothes. I'm not sure if that would work for quilting.
Look in your local newspaper for garage sales. In my neck of the woods, it is how some of shop. & folks here will advertise if they have fabric or sewing stuff at their garage sale.