They can be very economical. I made a good sized lap quilt using just one honey bun roll (1.5 inch strips) and a cream colored solid. The honeybun was on sale for $16. While it would have been cheaper to buy yardage of another solid, it would have made a much less interesting quilt. With the precuts, you get a nice array of coordinating fabrics without overbuying.
Here's my lap quilt made with the Patisserie line by moda: