If you live in an area you can free-range them, that would help greatly. When we are on a tight budget, our's free-range, get whole corn and whole oats in the evening, and have access to oyster shell. Our's do not get get corn or oats free-choice, only a few handfulls thrown upon the ground before bed(helps remind them where to roost). The oyster shell they have access to all the time. They are allowed to freerange from early in the day to late in the evening, and are locked up safely at night.
They get mealworms and kitchen scraps. Production is as good as ever! We get an egg everyday from each hen and the hens are in their second(!) year of production.
Another good place for cheap protein is using buckets of roadkill to grow maggots. You hang the buckets in the coop and the chickens will gobble up falling larvae before they become flies. This isn't suggested if your coop is near anyone's house! You can also compost worms or farm mealworms. All are great ways for "free" protein and the chickens love it.
If you are near any farms ask them how much they sale their corn and oats for. Our local farmer sells whole corn for $10 a 100lb bag and $7 for 75-85 lb oats.
Free-ranging is the best way to save money on feed, but it's not an available option for everyone. With free-ranging, expect losses to predation, it happens.
Have any other questions, feel free to ask! I'm all about saving money..LOL
-Kim