I usually save by:
1. Chickens I get in incubators more often than I buy
2. I often use vegetables from the garden (boiled potatoes)
3. In the summer, chickens have a place for walking, where they catch beetles, dig worms.
4. I feed them fresh kitchen leftovers, some bread, milk, boiled cereal.
My main food for birds is often just grain - a mixture of wheat, sunflower, corn, millet, barley and ground shells, or chalk.
I am afraid that the information on prices will be absolutely useless - I live in Russia, this is another country

. But i can write my useless infromation, of course
A bag of grain (40 kg) costs 550 rubles here, this is near of 8.5 $.
I spend on grain for 10 thousand rubles a month, this is near of 147 $.
But I have not only chickens, I have 12 goats (5 adult and 7 young), who eat not only hay in winter, but also oats (i buy it), I also have somewhere from 30 to 50 geese (if you count with small goslings), 30 to 100 ducks (if you count with little ducklings), and about 50 chickens leghorns...
In the summer I spend half as much on food as in winter. This is a very average figure, because I buy a lot at once, at a wholesale price, grain and other feed, I keep a whole supply.
Some my animals are my pets, another are for my kitchen (i never buy meat, milk or eggs in any shops). But i don`t sell anything, i am not a farmer.
I do not use feeding norms, I just put buckets and pots of grain, and see that they are not empty. Therefore, I have enough fat geese and ducks.
At local prices, 10 thousand rubles a month is a small amount of money; here it’s about 4 times to go to a good restaurant, or 10 times to a simple very cheap cafe.
Therefore, given that animal husbandry brings me a lot of different foods, then keeping a bird, goats and other animals is very profitable. But I noticed an interesting trend - the more, the cheaper. It seems strange to me, but it is because when I had very few geese I could not eat them, it was dangerous, but now there are more of them and I can choose a few geese for meat without much damage to the herd.
Even in the local climate it is good to have a warmed barn, because in a cold barn in winter the animals will eat much more to keep warm.
For meat, I usually choose those animals that are worse, and those that are better - leave.