Umm, last time around they were like $12 for 50lbs if I remember correctly.
If possible, I would rather use wheat and/or milo in the ration as those I can obtain for "free". I can add a little corn in though if necessary. It's only like $5 for 60lbs.
I can't see any reason you could not make your own. When I was a kid my folks at mixer/grinders and even an old hammermill and we made all our own feeds, We raised corn,soybeans sun flowers, rye and oats. I do not know the exact mix my Dad made but we always had eggs and fat happy chickens to eat. I know some will say you cannot feed soybeans to chickens, but we did it and it worked for us.
The only thing we bought was oyster shells for the calcium. I know when a cow freshened we fed the milk first few milking to the chickens and pigs. If I had milo, wheat and corn available to me now, I would not buy a feed. BUT I am considered old timer by many on here.