I'm not sure about Pedigree, but I know a lot of other foods have a frequent buyer club! A lot of good foods like Natura foods (Cal Nat., Innova, Karma), Breeder's Choice (Pinnacle), Canidae, etc. Most of those are buy 12, get one free.
"The dog has seldom been successful in pulling man up to his level of sagacity, but man has frequently dragged the dog down to his."
I don't think I would say Pedigree does more harm than good. I fed it to mine for a while and it was actually an improvement over Science Diet and Eukanuba. The latter two caused skin problems for my dogs. There are certainly better foods out there, though.
The rating on a good dog food should be in its ingredients not on the marketing. Look for a food that has a recognized meat source. Ex. chicken meal chicken, lamb or lamb meal it is preferable that it is not a by product as they can have inferior cuts in them such as feet beaks and other.Corn is not a good protein for a dog and is used as a filler. Corn is hard enough for us to eat let alone a dog the is a carnivore. Rice would be acceptable but I prefer a non grain food. Preservatives such as BHA,BHT, ethoxaquin are canceragens. Research on dog foods. It is a nasty world out there in the dog food industry and there are many tricks that the companies use to fool you. One good resource I found is The Dog food Project and also dogfoodanalysis.com Have a look and learn about what you are feeding your dog