What is the cost on a feline blood transfusion?

Sorry I didn't add more details earlier. i have been taking my cat to the vet. It's just when I posted the question it was like 2am and I was waiting for my vet to open. She ended up sending me to the emergency hospital anyways. I just got back a bit ago and it was $400 for the transfusion itself. I didn't care what the cost was but I just needed to make sure I had the funds when I went in since you have to pay upfront. He needs a blood transfusion because his body was destroying his red blood cells, essentially an immune disease/anemia. The prognosis is not very good and my heart is breaking at the thought that I might have to put him down if this doesn't work. The transfusion is the only way to buy him time so they can figure out what exactly is wrong with him.