dudes, one noob q

why is it sometimes, or most of the times, the cheaper cpu's can be faster than the expensive ones

like the Q6600 or its predecessor E6600, is the best performer compared to the QX6800 or the AMD X2 6000+ better than the more expensive intel counterpart?

or the E series or the Pentium Dual Core is better than AMD X2 or the FX series?

just need a basic answer