Differential problems

I own a 1.6 L Octavia I 2003 automatic transmission since 2003 and the car is simply wonderful. The car has 50,000 Km mileage in about 4.5 years which I consider as a very light use. I have been doing regular maintenance to the car and never experienced any problems. Unfortunately, a few days ago, I have been hearing a whine while driving the car over 30 mph. After taking the car to Skoda dealer, the problem has been traced to a fault in the automatic transmission mechanism. The list of the faulty parts is as follows:

1) Differential housing with output gear.

2) Output Shaft.

3) Taper roller bearing.

4) 1 set: Differential pinions.

5) Oil seal.

6) Support ring.

I am very much surprised to see that I have to change such major and expensive parts after only 50,000 Km. I believe and expect that those parts should last much longer than 50,000 Km, I guess they should last like forever.

Has anyone had simialr problems??? Please help.