I have an intel i5 6600k, however there is also an intel i5 6600, there is no difference besides my k model can be overclocked, it is as simple as flicking a switch for them to determine whether the 6600 is able to be OC or not. that being said they do make sure that the k models are the better quality of the bunch, this usually makes no difference noticeable difference if you arent OC the cpu but its adds a little reasoning to the cost difference, however most of the cost is just profit for them, which is fair enough, its their product they have the right to charge what they want, and if they didnt have oc and non-oc models then the price would be somewhat of an avg therefor those who arent going to oc are spending money which they otherwise wouldnt have to.