At the thickness of a bicycle disc rotor, they bend ... period. No amount of money will change that. A ceramic rotor would not bend, but I'm not sure that material is strong enough to stay in one piece at that thickness (they would shatter).

The most expensive rotors out there are titanium. Titanium is more "springy", it will flex farther and retain it's original shape. However, I've read accounts that they wear VERY rapidly. I'm not entirely sure about this as I've also read reports that titanium chain rings last forever.

Any metallurgists out there like to weigh in?