VR Zone heard the 55nm G92 GPUs from NVIDIA will be about 20-30% cheaper to manufacture. They also write these chips will be able to match the performance of AMD's upcoming RV770 GPU:
Nvidia G92 yield rate isn't good so per chip production cost is about $100. There are many variants of G92 out there and 8800GT is only one that Nvidia is selling at a loss. Nvidia has to shift to 55nm fast to lower cost. The new 55nm G92 is said to cost about $70-80 and performance wise will be comparable to RV770.