Don't buy precuts. Just buy yardage and/or fat quarters.
#1 - precuts are more expensive because somebody put more labor into cutting and packaging them. (Cutting is one of my favorite activities, but I know I don't speak for many)
#2 - what if you wanted to do something with 5" squares and a 2 1/2" strip from the same fabric? You can't do that with a jelly roll.
Maybe find one or two fabrics that coordinate with something you already have.