Figure an hour diag, $60-70, depending on his rates.
An hour or two labor to put it in, $60-140, again depending on his rates.
Napa's cheap bearing is $135. I've seen the OEM unit priced up to ~$320.
So if we assume you paid an hour diag (assuming you took it in for a noise), an hour to have it replaced, and the guy used a Ford unit (we'll say he paid $275 and marked it up 20% which is about average for my area at least), plus any applicable taxes puts us right up the middle of the $500-600 range.
If you have your invoice post up the breakdown of the bill. If you don't have an invoice, you are a fool.
The other thing I have to say on this matter is this: Nobody can force you to approve a repair. You are presented with an estimate, you approve or decline the repairs. If you don't like the price, don't approve the repair. If you do approve an estimate, get the work done, pay the bill, and THEN decide the price was too high and want to complain about it, well I have a 100 acres of woodland out behind my house. Feel free to hike out to the middle of it and complain to the squirrels because those are just the worst kind of people to have to deal with in this business.