I suppose that running the stuff through a roller mill to flake it, costs some money. Although I can’t imagine it is more expensive than malting and all that goes with that. Then again, there may not be as big of a market for the flaked adjuncts so that is driving prices up.
I agree that the cost effective way to go is to use regular old corn or rice in the form of corn meal or dry rice that you can “mill” in a blender. You just need to do a cereal mash first, not that big of a deal.
I checked with my supplier (he does a group buy sort of thing every other month and rotates who he buys from for variety) and the flaked corn is just over $1/lb sack price, flaked rice is about $1.25/lb sack price. We ar3e getting pretty good prices on sacks so I think this is kind of the best you can hope for as far as flaked product.