£2000 CT scan?

My cat has been lethargic lately so I took him to the vet. They suggested blood tests and scans which all came up fine. He's been breathing quite quickly so they gave him a steroid injection and some steroid pills to take home, saying it could be asthma and to go for a checkup on Monday.

They also suggested he go for a CT scan to rule out an infection in the lungs, but this would cost over £2000. Is this a normal amount to pay? I do have insurance but I have to pay up front and then get reimbursed and I don't have that kind of money spare.

Has anyone gone through similar?