I'm a bargain hunter. That definitely does not mean I buy cheap fabric; a bargain is excellent fabric at an excellent price. Half or more of the fun I have is finding a "treasure", i.e, a great piece of fabric; then, over time, I find matches for it. Sometimes, I put no effort into finding the matches until I see which quilt pattern I want to use the 'treasure' for. I've never bought a coordinated design selection and probably won't. I've seen some I really like, though.
As for your question: are you making a mistake not stocking less expensive fabrics? ... only you can answer that ... if your business is flourishing without the bargain fabric, then perhaps there's not much point in adding it. I shop where there is a wide price range as well as a large fabric selection.