I contacted a company in US that specializes in this and they told me that a low energy house of that size would cost 200 000 dollars at least in US. Why is there such a vast difference in cost?
It's the same as the words organic and food, green and energy useage, and exclusive and apartments. They are words that mean the customer will pay more. It's assumned to be high demand, so high costs are the result even if parts and labor are the same price.
Add a plain old audio jack to a car and you can't raise the price. Label that same jack an iPod connection and you can charge $200 extra for it.