It depends on where we buy the fabric. Sometimes ordering online is less, or when there is a sale. Like you said it also depends on quality. JoAnn's Fabric Shop has fabric anywhere from $5.99 to $13.99 a yard. Some of the cheaper fabric isn't all that bad. You have to feel it. I've bought fabric from Quilt Shops that weren't any better than JoAnn's.
I'm not sure this answers your question. but I buy if on sale or really really need it.