Remember that UMC has lower cost/wafer, but lower yields traditionally. At the same time, 55nm yields should also lag behind 65nm yields slightly, but I'm not sure the difference would be as substantial as between TSMC and UMC in general. And then again, yields don't mean much when you have potential redundancy nearly everywhere and that you can have plenty of bins to counteract parametric yield loss...
Overall, it should be fairly obvious that in terms of 'raw chip' cost (excluding package and testing which are harder to compare), RV670 is slightly cheaper than G94 (but probably by a bit less than the 240/210 ratio would imply). Where things get really hard to compare is when you factor in NV and AMD's different redundancy mechanisms, which both have advantages and disadvantages.
Also, these numbers are obviously better than those at expreview. CoJ and Crysis are especially good, and both are AFAIK quite ALU-heavy especially at high resolutions. This makes me suspect that we *are* looking at a higher ALU-TEX ratio than on G92 here; although whether that's via 96 SPs or a better config (consistent 3 flops/SP?) is a much harder question to answer.
P.S.: PCOnline consistently tends to overestimate chips' die sizes I think. My expectation is that the 'real 'die sizes are probably "~(192/210)*die size" for everything.