if you are eating eggs at your house as most of us do you could even use an attitude adjuster and grind up the egg shells and give them that instead of tossing them into the garbage, oops sorry if you don't know what an attitude adjuster is that's a rolling pin, mom calls it a hearing aid lolAdult chickens should eat about 4 ounces of feed daily, the younger ones less. For the sake of argument, we'll say they each eat 4 ounces of feed daily. You need 5.75 pounds of feed per day to feed your flock of 23 birds. We're gonna round that up to 6 pounds a day, and 30 days a month, and we get 180 pounds of feed per month. If they're blowing through 300 pounds of feed monthly, then they're wasting 120 pounds.
Of the 13 adult birds that you have in your flock, 5 of them are roosters. That's 4 roosters too many (and 5 roosters too many if you could care less about having fertile eggs). A savings of a pound of feed daily, 30 pounds of feed monthly, if you didn't have four of those roosters.
I'm getting 40kg (88 pounds) of 'all flock' feed for $22 per bag, breaks down to 25 cents per pound, which figures out to less than $2 per bird per month (at 4 ounces of feed per day). I put their feeder on a lipped cookie sheet, anything they kick out of the feeder that they haven't eaten off of the tray gets dumped back into the feeder for the next day's feed ration. When it's dustier than I (or they) like it, then I mix it with sardines, tuna, yogurt, mashed hard boiled eggs, moist fruit like watermelon (to pick up and hold the grain), or table scraps and call that a "treat".
I recommend that you use an 'all flock feed' or 'non-medicated chick feed'. Neither of these mixes contains too much calcium for your rooster, non laying pullets, or your chicks. Calcium supplement served in a dish on the side is typically only eaten by your laying hens, as they seem to understand that they need it; your other birds might nibble at it once or twice, but tend to ignore it, knowing that they don't need it. I cannot get oyster shell here, but my feed store sells ground up egg shell and my girls love it.