Hi, The bolt that holds it on and the cable bolt are carbon bolts. The bolts that could be out of aluminum went on. The pivots are Ti. The spring is Ti. The pivots for the arms are hollowed out. It's pretty hard to explain everything at once. Maybe a few points at a time.
I used to use Shimano, but ran into problems with the overall design being clunkier. Like the cage. How can I tune a Shimano cage to be like the Campy. They are miles apart.
So I switched over to Campy. This stuff takes a long time to do. I'm not going to tune an inferior design.
Mike, you're right, the plastic piece is there to prevent wear. But I don't ride my bike with the front derraileur rubbing. If it is rubbing I trim it. Some people don't care or are hard of hearing.
Some of the parts are overbuilt because of mechanics who overtorque bolts. Some are overbuilt because of riders who abuse the equiptment. Some of it is just because it is easier to manufacture.
Taking those thing into account, there is alot of room to tune these parts and still have a long lasting part.