Oh sweetie, I hope your kitty is okay!! Most vets these days have finance options for big bills, you can apply for finance and it's like a loan - you can always give it a go if you are quoted a big bill.
In my experience, no, vets are really understanding that families have heaps of bills to pay and won't make you feel at all bad about making a choice purely because of $$. I'm sure most vets would rather see a beloved pet put gently to sleep because of money issues, than kept alive and in pain because the owner can't afford to treat them, kwim? They are usually really understanding and sensitive about these things (at least, the vet I take my little fur-children to is always very kind).

I really hope it's nothing too serious and that the vets can help your cat get all fixed up, for a price that works for you guys. Let me know if there's anything I can do to help, okay??
xo