Dry, Canned, Moist, Home Cooked, Raw-the availability of pet foods on the market (and the opinions on how they should be fed) is as varied as a giant box of crayons.
With the melamine poisoning scare that affected many brands of dog foods a few years ago, we've learned that we can't always trust manufacturers either.
Asking a vet isn't always reliable. Most vet schools are sadly short on supplying nutrition classes, and many of those classes are taught by-you guessed it-pet food companies!
***Note and disclaimer on the above statement. There are some vets who study nutrition extensively and can do a good job with a nutritional consultation. And there are pets out there with medical conditions that need to be fed special diets because of it. In these cases, it's worth it to stay with their feeding protocols.***
The truth is there isn't a one-size-fits-all answer to feeding. Certain breeds, ages and medical conditions have different nutritional needs, and it's up to those who pay the bills to do our homework and choose wisely.
I will share some advice given to me when I got a new puppy years ago: Avoid foods containing corn, wheat and soy. These are cheap fillers and common sources of allergy problems and hot spots. With the biodiesel demand, corn is not such a cheap filler any more. Foods without these fillers mean you need to feed less, have less poops to deal with, and have less chance of obesity issues. There's plenty of foods available on the market that don't contain these fillers and it's not hard to find one in your budget.
Still think it's too expensive to feed? Do the math. Compare what it actually costs you to feed a cheap filler laden dry food with a more expensive meat based food without fillers. Compare cost per serving or day. If you have to feed less food and buy less bags, which really is cheaper? You don't have to buy the most expensive available-there are plenty of decent quality foods available in budget range.
Cats have different nutritional needs, and meeting the minimum standards requires more expensive ingredients, which is why buying cat food requires taking out a second mortgage to do so. I'm often asked "what can I feed my cat so it's poop won't stink?" There is no good smell that comes from a cat. But if you have litter boxes in your house, the food you feed can make a great deal of difference in the smell. Cheap filler laden cat food means that every neighbor in a two mile radius knows you have a cat. More premium meat based foods mean that as long as you clean out the box, you may not smell cat unless you're in the room with the boxes in it.
So pack up your reading glasses, hit the pet food store, and be prepared to read some label ingredients. If you're switching foods, get the smallest bag available. Do NOT make an abrupt switch unless you really like dealing with cleaning up the squirts. Mix a small amount of the new with the old, gradually increasing the proportions until you're feeding all of the new.
Because you can't afford to pay upwards of $50 a bag for pet food does NOT mean you love or care for your pet any less than those who can. The trick is to feed the best quality food you possibly can with your pet food budget.