OK, so you ARE upgrading.... Ate and Zimmerman also make a higher performance brake rotor, and they are also more money.
I cannot look up parts here for a car that is not sold here, so I cannot tell you apples to apples.
I know that VW list price for front rotors for my Passat are nearly twice what the 'standard' Brembo brand rotors I can buy from Worldpac would cost. I am pretty sure that Zimmerman (the gray coated ones) are who supplies the OEM rotors for my Passat. I will probably have 200k miles on my car before it needs front brakes, though.
The Ate Powerstop line is about the same cost as the OEM ones, IIRC. Then there is a step up from that in Ate but I forget what they call them. Zimmerman also has some performance version, I have never gotten any so I am not sure what is different.
Balo is a cheaper line, but made in Germany and certainly better than any Chinese parts store crap. They are not coated like the Zimmermans, but fit well and work fine (never had any complaints).
The two-piece Brembo rotors ARE expensive, but again being the same friction area I think it may be more bling than anything, unless they are embedded with some exotic substance. They may also have some cryo treatment to reduce warpage as well. I do not see much warpage problems with these cars though.
