My dad grew up on a farm. I grew up in a small town. Animals die. Sometimes of old age, sometimes due to sickness and sometimes in order for us to have a hamburger. I was brought up with a practical and respectful understanding of an animal's mortality. You shoot spring hares because they damage the crop. You don't shoot pigeons for fun.

If I own a pet, its life is my responsibility. If I do bad, it suffers and that is on me. If my dog is terminally ill or was hit badly by a car I would rather put it down than go for the long shot. I would cry all the way, but I would not extend its life just because I love it. Its quality of life is my responsibility and therefore ending it is my duty if there is no realistic chance of it recovering.

That being said I would have been torn two ways about your cat. That's a lot of money, but it is a sure fire recovery for the pet. If couldn't afford the surgery I would rather have put it down than risk it passing a sewing needle.

I guess I would spend as much as I could justify. I won't go beyond what I can afford (which is the main reason I don't have a pet) and I wouldn't pay for a procedure that with a low chance of success or one which would leave the animal in pain or discomfort.