It's C for me too.
I don't say this as a possibility in the future but as something I've done already. When my second Golden, Irina, got sick, and she was sick from November'92 to June'93, I did everything that could possibly be done for her at the cost of several thousand dollars, and I didn't have pet insurance at the time.
I would cut back on any other expenses if that would help my dogs. But, on the other hand, I would not keep them with me if I knew they were suffering.
It's also true that some people, no matter how much they love their pets, just can't afford those vet's bills. I have seen and heard many heartbreaking stories about that.