Fred's Hens :
Let's use the price of corn as an index. $8 a bushel or 56 lbs. Soybeans $13 a bushel or 60 lbs. Add a mineral and vitamin pak and you have a good idea what the raw materials are for a hundred pounds of non-organic feed. If you are close to the source or local corn/soybeans, your price per 50 lbs of feed should be $10.
Paying $17-$20 for a 50 lb bag means you are paying a huge premium for the trucking, diesel fuel, handling, processing, bagging, marketing, multi-levels of profit, etc. That's the price you pay for being too far from the source of the basic ingredients.
Common ingredient feed companies use is soybean meal which is less expensive then soybean since the soybean have already been used to make vegetable oil.
Your grain prices seem a little high for corn:
Our local cash prices this morning are:
http://www.trupointe.com/grain/cash-bids/
Corn: 6.17
Soybean: 11.42
Wheat: 5.61
I'm not sure what the price if meal is today but it's pretty inexpensive where we get it.
This paper has a lot of detail on soybeans, history usage, etc...
http://www.soyatech.com/userfiles/file/tradeflow_manual(1).pdf
All that said, you can get fresh milled feed for about 1/2 the price of the bagged feed in the stores.