... try another vet, or emphasize to the one you're going to that you can't afford to pay that kind of money for a diet plan and any suggestions would be really helpful. Most vets I've gone to have sympathized with the 'I really want to help my pet, but I also must eat, myself' angle.
Seriously though, the answer here is to talk to someone that actually knows what they're talking about, i.e. a vet. Someone trained and/or experienced in treating animals will know better than, well, probably anyone else.
Also, vet's going to know whether the cat will hate the food or not. You're giving them money for a (hopefully good) reason.
As a general note, when an animal won't eat a particular type of food to
your preference, the proper answer is to keep giving th'animal that food until they do. Cats, dogs, they're not actually that picky, they just get used to certain things (especially if they can manipulate you into giving it!). They get hungry enough, they'll eat what you give them. Animal won't starve itself when there's food available, though they may not eat to the degree the owner prefers. They know their body better than you do, most of the time.
Or spoil the animal and waste your money, either way