With the Commercial or feed mills They are out to make money. As with Anyone who has a product for sale. I am a business owner as well. I wouldn't be in business if I wasn't competitive.
As the market goes up and down the grain goes up and down as well. So your feed will reflect that and also change with the market. If corn is cheap the feed will have more in the recipe, If wheat goes up there will be less in the recipe and so on. ever changing. It wouldn't be logical to keep wheat in the feed at a high percentage it would be too costly to be competitive commercially.
I don't need to be competitive. I would rather feed my chickens knowing what is in the feed rather than not knowing. It would be more consistent in quality.