Good hypothetical question!
A little thought...
When i was a child we were poor. We lived off food stamps and lived in a rundown home. I was 5 and had my first dog, a stray that came to our house. I loved that dog and she was my happiness and best friend, truly some of the only joy and love i knew. How can one deny another that joy and love for both just because of their income?
We didn't have much but we managed to afford dog food though no vet, in fact i don't think having a pet and going to the vet was popular until in the last 30/40 years. Nobody i knew took their dogs to the vet unless they had something extensive wrong with them. Dogs have been companions for 100's of years and vets not so long, yet somehow i believe their have been some truly happy dogs and just thankful for the companionship and love. I think saying a dog can only live (be adopted & not killed) if an owner can take him to a vet is like saying if you can't afford health insurance you need to be put down
Just fyi: My Renee (first dog) was a happy healthy dog until she passed at age 13yrs. And never saw a vet and i live in south texas, in fact most my dogs growing up lived tumor & cancer free with no illness and died of old age.
I don't think money is the issue for the dog. A dog doesn't care, it just wants love. As for money and abuse; I've seen the wealthy abuse a dog just as easy as a homeless can.
In the end a fee does not make a good owner, however i do understand that things need to be paid for but keeping an animal locked up or killing one for the lack of fee is horrible.
That's just my thoughts on the matter.