In my family, it would be the care of the pet that would be the primary determining factor.
I do have a friend whose cat has been on dialysis for a year. And although I love my cats dearly, I would let my cat go peacefully rather than do something like that to them. It's not like you can sit down with the cat and say, "Hey, I know this hurts but it's making you healthier over the long haul."
I wouldn't do something to a pet that I'd hesitate to do to a human. I once lost a macaw I adored because she was in cardiac arrest due to an infection and the vet offered to "crack her" and apply direct stimulation to her heart. Even if she had survived that, I knew the recovery would be horrendous for her. It's incredibly hard for humans to recover from it.
I often think that we are able to give pets more grace at the end of their lives than humans because for some reason, it's easier for humans to send their companion animals off with dignity than it is their grandparents.
I've spent a bit more than $2000 on a kitten. He's now been a faithful friend for 11 years. I have no regrets.
I don't think anyone should keep a pet unless they can cover reasonable vet costs. If you have a healthy dog and he gets hit by a car, you need to be able to cover the cost of casting his leg. If he needs $5000 of doggie ICU care, that's another story. If you can't afford to spay/neuter and provide regular vet checks, then you shouldn't get a pet.
That $2000 kitten saved my DH's life several years later. I wouldn't have the money I do now for animal care if that cat hadn't been there. The kitten became a ripple in the pond that made a difference.

Jen
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