I agree with the above.

I am not a vet nurse or a vet student but I am a Biol student (so don't know as much as Efjay) and as I understand it, correct me if I am wrong, dodgy breeding can commonly cause problems with hips, knees, feet etc. Is she overweight at all?

It does sound like a very excessive cost to me...but my only experience of vet costs is fostering some very sick animals over the years.

Vets in different suburbs DO have very different pricing, I have found. So def get a 2nd opinion.

Some vets also offer payment plans.

I think amputation is very drastic and will cause the dog way more stress than she and you both need. My dog had a toe amputated...just a toe!...and she was down and out for a couple of days, and was a bit unbalanced for a tiny bit. I was beside myself with just a toe going!

Is re-homing an option? You would miss her but it's probably nicer than amputation or euthanasia.