Overclocking plays a vastly different role in the computer industry today than it did 10 years ago, a time when overclockers were considered outlaws by manufacturers. Back then even mentioning overclocking could void your warranty and industry leaders like Intel were working to eliminate it all together.
In contrast, nowadays processor and graphics cards manufacturers have embraced the practice, touting high 'overclockability' as a feature and in the process using it to sell enthusiast oriented products at a premium.
Take the popular mid-range GeForce GTX 560 Ti as an example. Base model non-overclocked cards start at ~$229, but finding them isn’t so plain and easy as most manufacturers prefer to push their overclocked counterparts. While the Nvidia specification calls for a 822MHz core clock speed, you shouldn't be surprised to see outgoing models running at 900MHz or more for this particular GPU series.