The price of the eco-laptop is ¥118,800 (US$1,231) and the price of a comparable, non-eco laptop is ¥113,800. Therefore, the price difference between the two is ¥5,000.
The story has been corrected on the wire and the sixth paragraph changed to read:
Of course none of this comes free. The green PC will cost ¥118,800 (US$1,231) compared to ¥113,800 for a similar PC that doesn't include the green energy credits. That's a premium of ¥5,000 for the green energy version.