New Life Spectrum does not cost more than other food in my experience; one container lasts suprisingly long compared to other brands of pellets made of corn or of flakes made of sh##.
If you're looking for cheap, buy quality food in bulk amounts and freeze what you're not going to use in the near future. You can get 5 pounds of new life spectrum for $55 shipped to your door, and that will last most people a LONG time.