$500 is still wayyy too much. A new axle is $100 or less, and the knock sensor can be had for $20 off ebay, but even $100 or less from a parts store. The axle takes 20 minutes to install and the knock sensor take 10-15. So you were charged $300 for less than an hour labor, plus parts mark up.

I wish I could pull an axle in an 20 minutes..

I wish I could pull an axle in an 20 minutes..

Usually takes more time doing it in the driveway. But in a garage, with a lift and all the tools at your disposal, it doesn't take long at all. Especially when you do that kind of work everyday.