You have to know that overclocking isn't just "that simple". Overclocking the CPU too much leads to overall system instability since they didn't overclock the NB, SB and DAC's. Usually the South-Bridge and the DACs cannot function under the temps of -20C.
Also, the CPU isn't meant for getting past 7GHz, some less stable CPU's gets downclocked because they can't maintain a stable system at the designed clock, and they sell it with an different name at a lower price.
A good example is the Phenom II and the Athlon II, they are basically the same CPU, but if the L3 Cache of an "Phenom II" has a defunct, they disable it and sell it under the name Athlon II"
Hope it helps!