"I know how much a part of the family they become"

"it's been about 50/50 when I tell people how much hip replacement costs as to whether they would do it themselves or not"

I think that your two comments answer each other, it comes to be that the cost is not an issue for an animal that comes to be an equal part of your family.

We have pet insurance, but it wouldn't cover all - the only canine cancer centre in Britain is, as it happens, in Cambridge - unfortunately by the time he was diagnosed it was too late: But the whole family was keen to sacrifice something to come up with the cost of a course of treatment.