Dude, let the dog go. That is not an appropriate decision. If it was a person who was hit, then it would be ok to borrow at that; but I pay property taxes so the county hospital will fix the broken bones of indigents.
Unless the dog brings in income comensurate with that, like a high-end herding or show dog, it is irresponsible to spend that much on a pet. Even if you had the $4,000 sitting right there.
If I were judging your credit card application or a loan application and I had your post in front of me, I would be inclined to think that you did not make responsible financial decisions and not approve your credit.
The dog does not bring home money, but so do not, for example, overseas vacations or even going to the movies. Would it be irresponsible to spend money on movies or tourism because this money produces no income for the spender?
The dog does bring positive emotions, and the loss of a pet brings negative emotions. These emotions can easily be valued by a person (owner) way over the $4000.
There are many situations under which a person might spend $4,000 on a dog.
But we are talking about the specific situation in which you don't have $4,000 and intend to borrow it at 25% interest. In that case it is not socially acceptable to spend $4,000 on the dog. To note your other examples, it also irresponsible to borrow $4,000 at 25% interest to go to movies or spend on overseas tourism.
Note that I am not just claiming that it is unwise and irresponsible (it is); I am also claiming "social acceptance" in that society in some sense backs this up. My evidence is this: if you bring a child in need of $4,000 in care to a doctor, and don't have $4,000, the child will get the care; you may be dunned for the bills, but the child gets fixed.
You bring a dog into a vet, and you are indigent, the dog either gets given away to someone who will pay or it gets the needle.
My personal views go further, in that even someone who has $4,000 is being irresponsible by spending it on a dog (in most cases - a breed in threat of extinction or a highly trained dog might be worth it, I am sure many seeing eye dogs are worth $4,000 and not replaceable for that). But I know that many people hold the opposite, and would even say you should not own a dog if you are not willing and able to pay $4,000 on vet expenses.
If you have to borrow at 25%, then you fail the "able" part of "willing and able".
One of the things that will come out of the current economic situation is that our society is going to be less accepting of people who do things like borrow $4,000 to spend on pet bills.
I can think of thousands of reasons why I'd like to have that option.
On example:
My dog gets hit by a car and it will cost $4k to save her life. I have an extra $1k in my budget each month, but only $500 in cash reserves.
I'd pay 200% annual interest.
If I lived in a paternalistic "aarongough knows best" society, my dog would die.
Please don't be so quick to imagine that your preferences and resources (parents, friends with money, etc.) apply to everyone else.