Sure, the Costco pizza's just an example because I happened to be contemplating their calorie-including menu while standing in the grocery checkout line the other day. That's
expensive junk food and happens to actually have some vitamins in it, hidden amongst the grease and fat and colon cancer. Check out pop tarts for some real WTF junk food cheapness. Neighborhood of 10,000 calories in a box of 48 "pastries" (24 2-packs), depending on the flavor. Around $11 if you don't catch it on sale and buy the real deal instead of an off brand. Zero prep (can optionally heat, don't have to, microwave's about as good as a toaster so equipment's flexible if one or the other's broken or missing) and keeps forever.
I'm not advocating junk food, mind you. I just don't get why people say it's expensive and so poor people must only be saving time with it, at best. Sure, it can be expensive, if you're running around buying name-brand potato chips or something. It can also compete with bargain-hunter, ultra-penny-pinching healthy cooking, though, on a strictly price basis, while conferring other benefits (health not among them). Depends on what you buy.
Incidentally, the canonical junkfood-diet meat to accompany rice and beans is hot dog, not chicken. Easier to cook, comes pre-ruined so you can't accidentally ruin it during cooking, competitive with even very cheap chicken on price, keeps much longer.