Those two adresses are still the ones to go to. Those were the ones recommended by xwingyoda, and he surely was the guy when it came down to Lego in paris. The gallery Lafayette is the best from a tourist perspective as this usually is a place to visit during a typical Paris tour.
Considering the prices, it really depends on where you're coming from. If it's from the US, forget it, it'll be highly expensive compared to your standards.