I look at it like this. If it is going to be an heirloom or put in a show (which I would never do), then only top quality is what I would do. If some 9 year old is going to sleep under it with a dog on top of it (which I always hope my quilts are used) then I would go for the best of the cheapest.
Personally, I buy LQS batiks but I would not say they are the only thing there is. I just like the colors.
My Walmart does not have fabric. I use Joann's and Hancock's fabrics for charity quilts or craft projects. I am under no illusion, that 100 (or even 10) years from now, that quilt I made will be a priced family possession. My Mom is the only one that has ever kept one that I gave her long term and it certainly wasnt because the work was museum quality.