I have fed my chickens wheat berries for a long time and other than a little diarrhea in some of them, they appear to tolerate it quite well. Adding the corn and other grains certainly adds to their dietary variety as does soybean.
As for cost, check with the local grain elevator. The guy who wants $250 for his wheat is selling it at $10/bushel. That is really high. Most of the corn in this part of the country is going for around $3/bushel (58 lbs). If you and a couple of friends go in together and buy a hundred bushels, you'll have enough corn to feed chickens till the "cows come home" Adding wheat which will be substantially less than $10/bushel should do about the same thing. Interestingly, the fact about wheat is that if it is stored in a dry location and not allowed to get wet, it stores essentially indefinitely.
When I first moved to SDAK, I was broke and had no job. I went to the local grain elevator and had him fill the back of my P/u truck with wheat (winter hard wheat). I paid $133 for the entire amount and it came to about 2000 lbs. I figured, I might get tired of home-made bread (yes, I make that myself) but I won't starve. Between sprouting it, grinding the sprouts for juice and making bread and cereal with the wheat, I found that I would have a limited but really good diet. The roughage helped too!
So the answer is "Yes, you can feed wheat berries to the girls safely".
Don't buy a lot of grain from "retailers". They raise the price so high that you can't believe it. The farmer who works so hard to raise it gets very little for his effort. The elevator will sell you all you want (fill up your p/u truck) for very little money and you will have enough to last quite a while.
Getting it out of the p/u truck and storing it properly may be a little more challenging because you probably need your p/u truck for other chores soon after bringing all that grain home in it. That takes a little prior planning; but is worth it to be sure.
I heat my house with corn, and when the corn is low weight and the farmer is getting less than $2.41/bushel you can heat your home for about $240/year...yes I said a year. I go through about a bushel a day for heating my home.
So as I said, buy from the elevator, NOT the retail establishments. Even
www.waltonfeed.com from whom I get many of my stored grains and beans charges a lot for their grains which they sell in 50 lb bags.
Being prepared isn't that hard if you know a few tricks. In the immortal words of Louis Pastuer, "Chance favors the prepared mind".
Best
Trim
So shoot me...
Most Mormons (Church of Jesus Christ of Latter-day Saints) have at least some long-term food storage. One year's worth is the goal. Most in the US will store wheat because it lasts so long.
