There is no controversy about dental prophylaxis in cats. Cats with gingivitis and other dental disease live with pain and discomfort, may stop eating, and can seed bacteria to the heart, kidneys, and other organs. Bad teeth will seriously decrease the quality of life and the length of the life span. (Lions do not get their teeth cleaned because they eat whole carcasses – bones- and they don’t live long enough to have this problem.)
Ask for a breakdown of the estimate that you received. For that quote, I would expect the vet to be doing pre-anesthetic bloodwork (to check for problems before anesthisia), placing an IV catheter for venous access in case of complications, sending the cat home with antibiotics and pain meds if necessary. You haven’t mentioned how bad your cat’s mouth is – if she requires extractions, that will significantly add to the cost of the procedure.
Remember, this is a procedure that requires full anesthesia, intubation, and specialized equipment. If you (a person) went to an office and were anesthitized, intubated, monitored by an anesthetist, had a dental cleaning and possibly extractions and oral surgery, I can guarantee that the cost would be more than $450.00.