I tend to think that some quilt shops are owned by snobs and if you tell them or even mention that you have bought ANYTHING from any place other than a QUILT SHOP, they will gasp, fall down and melt away. (too bad that doesn't really happen. lol)
My point? You can get GOOD quality fabrics from other places than a quilt shop. Does that mean that a quilt shop ONLY carries GOOD quality? NOPE!
I don't know what manufacturers you are referring to that are making this "superior" fabric you are talking about, but I have found quilting fabric (Cranston, Timeless Treasures, Moda, Micheal Miller, Thimbleberrys and a few more) at Ben Franklins here in Guam. Now, yes they do sell some stuff I wouldn't consider using, but some others might use it. To each their own, as they say.
The fabrics that I have mentioned are also found at Walmart and some of the other little stores. (ones that the quilt snobs would die and fade away if they were ever in them)
So, we quilt with what we can afford, so if you can afford the GOOD SUPERIOR stuff, as you say, then that's good! Some of us are less fortunate and get what we can because it's either what we can afford or what is readily available to us because of where we live in the world.