NVidia had massive yield problems with the original GF100 Fermi. Hige die size and a brand new process caused them no end of delay, cost and supply shratages. What they should have done was release a smaller GPU / higher yield part first to test the water. That is exatly what they have done this time, but to be honnest, even NVidia must be surprised how everything come together. Massive GPU clock speeds, massive memory contoller performance, massive overall performance. If their GK104 part can beat AMD's top part, why not name it as a top part and cream in the porofit? It is what any business would do (I'm not saying I am happy about it).
So, GK104 was designed as a ~£250 part, but AMD's huge price hikes for the 7900's and their relatively poor performance has enabled NVidia to have it's cake and eat it.