They recognize your country of origin based on IP and calculates the correct VAT based on that. That's true for most stores in the EU. I see that you write in https://news.ycombinator.com/item?id=35447307 that the tax is not included. They state that “The price that you see includes estimated VAT. The exact amount will be calculated at checkout.”

However, based on the other products in their store it is the same for me in the store and at checkout. Nothing fishy about this.

This might very well be the case.