They are talking about this on Dogster too.
do all those show dogs really eat Pro Plan? - Food & Nutrition Forum
I really can't believe that "better" ingredients are not better for your dog.
I don't even know what some of the ingredients in Pro Plan are
.
And as far as "cheaper quality food" being $ cheaper it is not. There are plenty of better quality foods out there (even if they are not grain free). I feed my boys (right now) Nature's Variety Prairie Chicken. $12-$13 a 5 lb bag.
Even Natural Balance is around $14 for 5 lbs and Taste of the Wild is about $12 for 5 lbs.