I'm going to throw this out there. Chickens don't need very much compared to other animals commonly kept as "pets". You can throw a few bucks or a few thousand bucks into their care and it doesn't change their basic needs. My grandparents had a chunk of land, horses, chickens and a barn. The chickens free ranged all day long. They drank water from the horse trough and creek, ate bugs and scratch or scraps tossed from the back porch, and slept in the barn at night. Sometimes the truly brave or dumb ones would roost in the trees at night though it was discouraged. Once in a blue moon they might get picked off by a predator and those predators were dealt with whenever possible. They never spent money on a vet for the chickens, very little actual money was spent specifically for their care and yet they thrived and were the most content chickens I've ever seen.
There are some breeds that probably shouldn't be free ranged though. Now if you stick an animal in a cage you are solely responsible for providing every single thing for that animal and if you deny them food or water, deny them a clean environment, deny them care or attention when they are sick or injured.. that's when you do not deserve to own any animal whatsoever... has very little to do with the amount of money you spend on them and everything to do with how you manage your animals (animal husbandry). Also keep in mind because chickens are a livestock animal here in the US you can provide treatments without involving a vet, not sure how it is in other countries around the world.