The 5970 is a dual-GPU single-PCB part - it is two underclocked 5870s on the same PCB. Using your "fixed" chart, it becomes:
1. GTX 480 4-way SLI -- $1840
2. 2x 5970 Crossfire (this is 4-way Crossfire, btw) -- $1360
3. GTX 480 SLI (2-way) -- $920
4. HD 5870 Crossfire (2-way) -- $760
5. HD 5970 -- $679
6. GTX 480 -- $460
7. HD 5870 -- $380
3-way GTX 480 SLI (3 GPUs) is faster than 2x 5970 Crossfire (4 GPUs). SLI scales better than Crossfire. That's probably part of the reason that 3x 5870s is faster than 2x 5970s with inefficiency offsetting performance.
http://www.hardware.info/nl-NL/artic..._GTX_480_test/
ATI is not going to introduce a single-GPU solution for $700. The market will not bear it. More likely what you'll see is ATI selling a reference design for ~$500 - $529 with OEMs charging up to $600 for non-reference designs. ATI doesn't want to create a niche market for their top GPU - they want to keep pressure on NVIDIA so the likelihood of a
reference HD6000 at $600 is almost nil. Note that I am making the differentiation between ATI suggesting the MSRP of $500 and online vendors taking advantage of product launch and product shortages to jack the cards up $200 over their MSRP.
Don't expect to see too much movement in the 5870 price. The reason for that is that AMD meets with its partners and informs them of its plans (hence the HIS leak earlier this week) so that the OEMs aren't left with huge volumes of old product. AMD could potentially hold off on launching its new product until existing stock of 5870s declines.