'90 300SE Air Intake Pump?

After hearing a noise from under the hood of my 1990 300SE,120000 miles, my mechanic has determined that the Air intake pump needs to be replaced, the cost of a rebuilt being $500.00+. Is this normal for a car of this mileage? The noise was like that of a coffee grinder, especially loud right after the car was first started. Thanks!

[stevebfl]

We have replaced a number of A.I.R. pumps on 103 motors. It is strange as I don't think we have ever replaced one on a 380 which has a similar pump and would be much older. The bearing is always what fails. I would have to assume that the belt puts more of a load on the 103 pump. Then again the 380 can have its belt removed where as the 103 can't so maybe there have been some 116 failures that I didn't notice.