For those of us who have a pet rabbit (rabbits may not be as common as cats or dogs but they make super sweet pets), the cost of rabbit food can get quite high because, let's face it, whose bunny does NOT eat a lot? My rabbit eats more than both my cats combined.
Walmart sells a 25-lb bag of rabbit pellets for $7.99 which is VERY reasonable. You can pay that much for a much smaller bag at Meijer or Kroger. The food is just pellets---it doesn't have the tasty little treats that some of the other foods have---but as long as you are feeding your bunny fresh food and some hay besides the pellets, they really don't need all those little treats.
Walmart also has the least expensive hamster/gerbil food, cat food and cat litter that I have found. We feed our cats the Good Life food and they sell a 6-lb bag for $6.99 (Kroger sells the little 3-lb bags for $5.99!!).