I often buy remnants from my LQS and cut my own precuts. I cut 2.5" strips, 5" charms, 1.5" strips and 10" squares. I have plenty of variety at less the cost of prepackaged precuts. I have bought precuts from Craftsy when they have clearances sales especially on their kits. You get lots of fabric (sometimes 10-15 yards) in the kits for about $3-$4 per yard average. Whether you buy precuts all depends on what you are making and what fabrics you have available to you.
I even cut my own solid background strips from yardage. Bella solids are $4.95 a yard at Thousands of Bolts (or you can buy Kona solids from Joanns) and it takes 3 yards to get the same amount of 2.5 strips in a jelly roll. The jelly rolls are $32-$40 dollars for 42 strips versus $15.00 if I cut them myself. I use my strip slotted ruler which makes it much easier to cut the strips.