I once saw a line of fabric in WalMart that my local quilt shop sells. I asked her about it, and she told me that fabric manufacturers print different grades of the same fabric. That way they can sell quality fabric (more expensive) to quilt shops, but still be able to sell to discount stores who want lower priced fabric (it's also lower quality). I think the old adage holds true - you get what you pay for. :-)
Check out these sites:
http://patsloan.typepad.com/quiltershome/fabricq.html
http://www.quiltropolis.net/articles/quality-fabric.asp
http://www.camplebanon.org/uploads/f...tips%20pdf.pdf