Premier designers tend to design for premium fabric companies. World-class design brings a unique dimension to premium quality fabric. It comes with a price, but it adds immeasurably to the special nature of quilters' grade fabric. There is one more point that should be addressed. That is the issue of service and expertise.
Most shops provide classes and expertise unmatched by the chains.
Quilt shops and mail order catalogs generally do not sell jobber goods. They offer only first quality, premium brands at fair prices. These firms deserve your support. In conclusion, there is most definitely a difference in fabrics. You get what you pay for.