I've heard the Costco (Kirkland) brand is decent food and reasonably priced.
You have to remember that with cheap food, although you're saving money in the short term, there's a chance that eventually the vet bills are going to add up when your pups get sick due to the low-grade ingredients. English bulldogs are very sensitive in terms of nutrition. With more expensive brands, you wouldn't need to feed as much as you would with Pedigree. So you can be saving that way as well.
Cooking food for them can save you money too. Maybe prepare 3 or 4 days worth at a time so your parents will only need to take them out of the fridge, put in the microwave if they wish, and serve. But remember, don't feed any cooked bones. They turn brittle when cooked which can choke our pups. I feed raw and find that chicken, ground beef and pork are the cheapest types of meat. You can also add veggies and fruits to your mix instead of rice.