I have 10 birds and layer feed is about 15 dollars for 50 pounds, scratch is similar.
I spend about 40 dollars a month feeding them.
I give them oatmeal and kitchen treats too. Nothing icky or rotten for them at all. I actually buy specially for them.
I steam broccoli for them since they like it cooked better than raw. In the summer I get them watermelons and cantalope as well as fresh corn on the cob.
The 40 a month is including these items.