This. I like the "used car" analogy. I don't care how fast somebody got it or how much abuse they may have put it through; it's still used, and definitely not worth a premium over the same thing but new.
The difference between a car and a chip is that, well, how are you going to do the equivalent of overclocking a car? Certainly the analogy holds for possible wear and tear, as well as for possible damage, but as for getting extra performance from the stock parts... not so much.
A chip that hasn't been on suicide runs, but has been proven to overclock to x-amount with a particular motherboard and so many volts at such and such a temperature is certainly more valuable than a retail chip if you intend to overclock it. The retail chip you get hasn't been exposed to high voltages, but it may also refuse to go beyond a few hundred extra mhz. A nicely overclocked chip shouldn't be much worse for it, and will pretty much give you a guaranteed clock. That is worth something.
