Sick Cat

I don't mean to be trivial, or boring, or even stupidly obvious -- but when a pet gets seriously ill, it can be hideously expensive. I never thought about pet health insurance, but now I wish we had some. 800 dollars so far for a bunch of tests and overnight stay at the pet hospital, for observation. This morning they say they see an elevated white blood cell count, indicating infection. And now more tests today. They still don't know what is wrong with the cat. What can you do?