Well, there's reasonable and then there's what I am willing to pay most of the time.
Reasonable at quilt shops near me seems to be 9.99-12.99/yd. Clearance prices are 50% off.
If I have a particular quilt in mind for a special someone or occasion, my upper limit is $11 for a focus fabric, and then I tend to pick out coordinating fabrics that are less than $8 if I can. For donation quilts or pillowcases, I don't like to pay more than $5/yd.