NVIDIA didn't release details regarding the physical size of the GeForce GTX 460, so Nordic Hardware decided to get the data the hard way. The site confirmed the rumors of a surface area of 366mm², which is about ten percent larger than the surface area of AMD's Cypress GPU.
Early information has claimed a surface area of 366mm^2 with GF104, which is confirmed by these pictures. You can compare this to the 334mm^2 of Cypress and simply it means that NVIDIA can't make as many GPUs per silicon wafer as AMD can, and that the GF104 GPU is still more expensive than AMD's most expensive Cypress chip. This is no matter the quality of the manufacturing ot day, where AMD probably has the advantage with its more mature technology.
Keep in mind though that GF104 is sold at around $240 with GeForce GTX 460 1GB, while AMD is selling Radeon HD 5870 for around $360, even though the chip is considerably cheaper to manufacture.