That is an odd definition of payback. The raw material cost of creating something is irrelevant since you cannot buy anything at cost: there are always value-add processes and profit margins to consider.
That said, the GP is right, unless these wind turbines in the study have noticeable improvements compared to other turbines I would expect there to be similar installations around the country that are making profits/savings for their investors. There should either be news about those gains or news about how the investors who previously built wind turbines are investing even greater sums of money due to their success.