1998 Cadillac STS alternator

Hi,
I have never had alternator problems, the car is 10 years old.
I heard a very loud noise when I turned the engine to start.
When told this the mechanic immediately said I need an $700 alternator, plus he said the voltage was at 11.

Now is it possible I need bearings because they are bad in the alternator instead of buying a brand new alternator.
Would it be cheaper to just replace the bearings in a car like this?

Thank you
DMR