The best AND the cheapest food for my cats has been homemade. There is an initial investment in supplements (bone meal powder, kelp powder, cod liver oil, vitamin E), but it lasts forever. My two cats have more than enough to eat with a weekly purchase of 1 3lb package ground turkey, cooked just till done in olive oil, then cooled, pureed with a small amount of water and raw veggies, and supplements added. They get a scoop of that 2x a day. The weekly cost is only about 4$ for the turkey.
I'm sure something similar could be used for your dog.
Then the dry food can be kept as a supplement or treat, not the bulk of their diet.
Also keep in mind, dry kibble isn't best for cats as their main dietary staple--cats just don't get enough liquid that way and often wind up with kidney and bladder problems. T