I am not a fabric snob at all, probably 75% of my stash comes from JAF. In fact, I picked up several yards of flannel from JAF the other day.
That being said, my mother worked as a seamstress for a time at a garment factory and they made jeans for a certain well-known brand for various retail companies. When they made the jeans for the mall stores they used one grade of denim and when they made the jeans for the walmart stores they switched to a lower quality thinner grade of denim. Both jeans carried the same well-known brand.
I can't help but wonder if Waverly is doing that for it's Walmart supplier. My personal take away from all of this is that I look at fabric quality before I buy, wherever I am buying from, I've seen good stuff at JAF and WalMart and crappy thin stuff at local quilt shops. Bad quality = pass