Jeanne is dead on. When I first started quilting I didn't know any better either. I figured cotton fabric was cotton fabric. Even though I had sewed garments in my youth, I never paid much attention to fabric. So when I started my quilting journey 25 years ago I went to my local JoAnnes and bought their low end Keepsake Calico stuff for my first couple of quilts. The fabric seemed fine to me but it faded horribly in a very short period of time and a few pieces of it went threadbare and seemed to kind of disintegrate in some of my patchwork pieces. After spending hundreds of hours working on my beautiful quilts I wanted them to last. So I started paying attention and buying my fabric from other sources than big box stores. I loved working with name brand LQS fabrics like Robert Kaufman, Moda, Hoffman of California, Timeless Treasures, etc. After a while I started recognizing the type of fabric I liked working with and paid attention to the selvage marking so would know what brands I liked.
Now I feel I can confidently buy on line based on brand name. That isn't to say I don't get the occasional dud now and then but for the most part I can find name brand high quality quilting cottons on line in prices ranging from as little as $4 per yard if I find a good close out sale. On average I stay in the $7 to $9 per yard price.