Apple sells 64 GB of storage for the same money. 479 Euros (~$593) is due for the bigger 32 GB model.
That at least applies to the 16 GB version that should cost 389 Euros (~$482). Unfortunately, Google's customers have lost an affordable reference device in this category with the Nexus 7 because the Nexus 9 moves within similar price ranges as Apple's iPad Mini 3, and that is anything but cheap. That makes sense considering the applied screen size of 8.9-inches. Both the Nexus 7 and Nexus 10 have become unavailable in the Play Store since the new tablet was launched in the market. Google's Nexus 9 replaces two products of the American corporation right away. For the original German review, see here.