Personally I don't believe the reduction of wafer thickness is enough to compensate the rising poly price - just personal opinion. And SPWR is still in the early stage of production, wouldn't be able to catch up the manufacturing efficiency as STP and Q-Cell for sometime to come. SPWR does command 10% price premium for their high-efficiency conversion.
When SPWR does possess technology leadership, it is hard to say that how the market deal with the rationality of its price. I am buying through foreign dealer for Q-Cell, which is selling at less than 7 times EV/ 2006 Sales. STP and SPWR are selling at 11 times.
Beyond 2007, Poly price may no longer be an issue. We still need oil price to maintain at the current level to expect solar maker to continue to prosper.