I try not to pay full price if it is fabric to add to my stash...so for that I look for sales/clearance at less than $6. it helps to do the fabshophop because I often check the sales/clearance at the shops.
If it is for a specific quilt, I try to stick less than $10 a yard and try to bring in some stash.
But a lot will depend on your access to shops/sales and coupons.