My kitty J.D. had DKA soon after he was diagnosed, back in 2005. He was admitted to the University of Pennsylvania School Of Veterinary Medicine on December 22nd. He was in critical condition. I was amazed he even made the long drive to the hospital. I just kept praying and talking to him. I remember all I lived for each day was when I could leave work and go visit him, and taking the long drive to see him for 20 minutes each day. And each day he got just a teeny bit better. He had two transfusions while in the hospital. I don't remember what for.
He was hospitalized for 8 1/2 days. He was finally released on New Year's Eve and came home with a feeding tube because he would not eat at the hospital.
I had a line of credit account and was able to pay it off in about 6 months. The cost for his hospitalization was nothing compared to a human's bills in the same situation. If your cat is a fighter, keep thinking positive thoughts. I was able to visit J.D. everyday. He went from barely holding up his head the first day, to laying with his head up the next, to bathing himself the third day and sitting up a little bit, and then on the 4th day crawling weakly into my lap with tubes attached to each leg.
J.D. was 11 when he had DKA and lived to be 20. I have seen lots of cats make it from DKA in the years that I have been on this board. Food, Insulin, Fluids, and veterinary hospitalization if at all possible. Keep praying hard. I will keep Sebastian and you in my prayers, too. Keep fighting Sebastian.