Try your local Lidl for some cheap raw. Over here (Ireland) they have a box in the freezer where they put short date stuff at a reduced price. Set yourself a top price (like £1 a kilo) and buy everything that's cheaper. Add it up in your head because sometimes they shove it through the till carelessly and the full price sticker can get read instead of the reduced one.
I often get whole chickens for 2 euro but rightly or wrongly, I cook those in a pressure cooker and take the meat of as I don't trust the tiny thin ribs and the like. All else I feed raw and I add some "Gain puppy and saplin