Depending on what it is, it isn't healthy for them and will give them diabetes and make them little fatties (even if it's healthy for you!).
I give my dog a mix of meat on the bone, squash or carrots, and eggs (no fruit, added sugars, garlic, onions, avocado, or dairy, with moderate fat, and slightly higher protein than I eat).
My cats get all meat with no vegetables or fruits with very high protein (80% by calorie), including ground up bones, organs, and lean meats (mainly rabbit and poultry).
The main difference is that while dogs eat fairly similar to humans (literally evolved eating our scraps) they also get fat from similar things (junk food, too calorie dense) and shouldn't eat too much fruit or any bread or very high fat (can cause diarrhea).
And cats have very high needs for protein compared to dogs or humans because they are built to use it for energy (dogs, like humans, use carbs and fats directly and protein mainly for structural needs), and they need to eat it raw due to essential amino acids and vitamins that degrade or are lost from cooking.
In terms of cheap, it depends on how you do it. But it's definitely saved me ass loads of cash on meds and avoidable health issues. Kibble is basically junk food for animals, and I've turned around many of my adopted pets health by changing their diet and even took one dog off of insulin after resolving his diabetes.
