LAZ, having had a cat with lymphoma who went through bouts of being a picky eater (chemo has that same effect on animals as it does on humans), I can sympathize with you. (I have another with lymphoma now who's not finicky, and I thank my lucky stars!) There are a lot of people with sick cats who feed baby food (I've found that Gerber's chicken, turkey and beef go over best with my sick ones). Although I don't have any recommendations for you of inexpensive baby food sources, I do have some other tips for finicky eaters:
1. Have you tried microwaving the wet food so it's slightly warm to the touch? A lot of cats stop eating because their sense of smell has become diminished, so warming the food increases the aroma and, therefore, makes it more enticing.
2. Trader Joes sells a tuna fish designed for cats. (I can't remember what it's called, but it's in the pet food section.) A lot of people with finicky cats swear by it! Regular canned tuna in spring water is high in sodium, but if you buy low sodium tuna marketed for humans, you're probably getting a similar product. When my cats are being picky, I've found that tuna juice (i.e., spring water in which the tuna's been sitting) poured over regular cat food will make them eat almost anything. They usually like the straight tuna, too.
3. A lot of people with picky cats will start a meal by spoon feeding their cats a few bites of wet food to stimulate their appetites. If you put food in a cat's mouth (or even just get it on their nose, lips, whiskers, gums or paws), they'll usually lick it off and swallow it. If you then hold the food on a plate under their nose, even most finicky cats will eat.
4. Since you don't mention where you typically buy your pet food, I'd recommend a couple things. Your vet probably has a few varieties that include meats you wouldn't typically find at pet stores (deer, rabbit, pork...). Ask to buy a few individual cans of those. Also, although a lot of pet owners think it's generally a brand of low nutritional quality, they'll also acknowledge that Friskies wet food is the equivalent of "kitty cocaine." In other words, if you can't get your cat to eat anything else, they may still eat Friskies. Finally, if you've only been going to big chain pet stores, please check out some of the independent stores, which will carry some high-quality brands that you won't see at grocery stores, Petco/Petsmart or your vet. I particularly like the store Four Legs on the east side of Clark north of Racine. There are probably a dozen different wet food brands that you won't see at a chain stores, and the owner will also give you samples of dry food, too. (That said, the super premium canned food can be more expensive than baby food!)
5. If you decide to stick with baby food, please talk to your vet about getting a good vitamin supplement. You cat is missing out on some essential nutrients by just eating baby food.
6. I realize you said your cat is 19 years old, and has hyperthyroidism. You didn't say what kinds of tests your vet conducted, but you might want to ask for a referral to an internal medicine specialist. Of course, you need to ask yourself, if you find out that something's wrong with him, at his age, would you make the quality of life (and cost) decisions to treat it? I do know friends whose cats had hyperthyroidism and only after getting the radioactive treatment (sorry, can't think of the name) did their appetite actually improve.
7. You might also want to do a google search for feline and "assisted feeding," which will give other suggestions.
I realize this is a long post, but as you can see, I've been there! Please don't hesitate to PM me if you'd like to email privately, since I realize this thread is a bit off topic.
PS: To add to what Louisa said, some people also feel that cats shouldn't be fed food containing garlic, either. (You'll see that on the link she posted.) Ironically, you'll find both garlic and onions in some cat foods, too. More recently, I've read some articles that say garlic and onions may be ok for cats in small quantities if their immune system is OK (ie, the cat isn't at risk for anemia in the first place). But it is a controversial topic, and best probably best to avoid garlic and onion in an older cat.