I'm afraid that in the US, anyway, UPMC's number is probably low - I think many times it is over $50,000 - for me, Cyberknife certainly was.
One question on the Aetna quote: you listed it as a specific procedure number 61793. I saw the billing on my CK treatment, and it was broken down into many individually billed items: MRI, CAT scan, treatment planning, procedure each day, doctors each day, consultations, hospital fees, etc. Maybe that figure is for just one of the codes they use?
I would suggest you get someone at Aetna and someone at UPMC to speak to each other by phone, especially if you can also provide both ends with the radiologist report from the MRI, and a hearing test. Maybe if Aetna hears the actual list of codes involved, they can give you a better idea. $7,000 can't be "usual and customary" for any complete radiosurgery treatment, especially one involving neurosurgeons and the human brain.
I Hope you get some better support from Aetna.
Steve