"... is significantly more expensive ..." --- only $18 more expensive.
It's probably just a special binned part; since 2950x can hit 4.5 boost, it would make sense that they could also make some other chips that can hit these frequencies ... and it might make sense just to leave them in their stock configuration ... but offer better OCing for those who wish to pay a little more for a binned chip. $18 for a binned chip? That's about what Intel charges for their binned chips, isn't it? ...
If you leave it in stock config, you don't have to crank up the TDP or change the TDP rating metric to only consider base frequencies like the other brand had to. (So they can pretend to their fans that they still have cool and efficient chips compared to the competition. lol. A friend just built a new PC - his friend told him to avoid AMD because they run too hot and consume too much power - then I showed him the power consumption reviews and put the attitudes back into their rightful places. Yes, Intel's "95w" 8 core 16 thread can suck just as much power as AMD's "180w" 16 core 32 thread 2950x)- even the infamous FX9590 "bulldozer" CPU wasn't nearly as hot or as much a power pig as the 9900k).
That said, this promo seems like an afterthought more than an actual promo ... I guess everyone is waiting for zen2 and to try to really promote old technology with flashy advertising, big headlines an exorbitant pricing, would be something that consumers might just see as a lame gimmick to try to sell last year's technology. cough ... Intel ... cough