I said Oct. 25, 2010, not Sept. 22, 2010.
Also, I don't see why Barts XT components would cost more than 5870 components. Barts XT should be cheaper.
5870 vs. Barts XT cost comparison:
Both use 256-bit PCB VRMs and other such components (and some people are saying that Barts's PCB is merely the Cypress PCB with a tweak or two, to save on design costs) = roughly equal cost
allegedly both use same-speed 1 GB VRAM vs. 1 GB VRAM = roughly equal cost
5870 has a backplate that I doubt Barts XT will have = cheaper for Barts XT
cooling costs = if Barts XT has a 188W TDP like Cypress had, then it's a tie; I suspect that Barts XT will have a lower TDP though, given the smaller die size, meaning Barts XT probably has cheaper cooling costs (this is an approximation because power and cooling have a non-linear relationship, and more-utilized Barts shaders may mean thermal density problems that the less-efficient shaders of Cypress don't have, etc.)
Last but not least, the GPU itself should be cheaper to make. Assuming that Barts XT is 70% the size of Cayman, Barts XT will probably have a smaller die than Cypress (.7 * 1.17 is about 0.82, which is less than 1.0 the last time I checked), on a more mature 40nm TSMC process (i.e., higher yields) = cheaper for Barts XT
Are these cost savings enough so that selling Barts XT will be as profitable as selling $350 5870s? Perhaps not, but the thicker profit margins will be on Cayman and Antilles anyway.