Do you hunt or know anyone that does? If you do, getting the inner organs of wild game is perfect for the dogs. I always use them sparingly and try not to over do it with that stuff. It is very rich. You can also buy beef/calf liver and kidneys fairly cheap at most grocery stores.

As far as chicken, I've never fed the chicken necks. I always used the leg quarters and bought them when they went on sale. The bone to meat ratio seems to be good and I can get them anywhere from 29-39 cents/lb when they go on sale. Don't forget about feeding eggs. They seem to be a very under rated food source.