A Nexus 9 32 GB (Wi-Fi only) can now be purchased for as low as $299.99 from Amazon. At the same time, the 16 GB version of the tablet costs $290 - obviously, you would be crazy to get this one, instead of paying $10 more for the 32 GB model. Meanwhile, if you're visiting HTC's US website, you'll still find the Nexus 9 offered at its original prices ($399 for the 16 GB variant, and $479 for the 32 GB one), so, at the moment, Amazon is a better place to shop for the device - see the source link below.
It's likely that, pretty soon, Google will discontinue the Nexus 9 to make room for a brand new stock Android tablet. This could happen when Google releases the final version of Android N - sometime later this year. Of course, the Nexus 9 will be updated to Android N anyway, so you won't be left behind if you're buying the tablet now.
Google Nexus 9
source: Amazon via Droid-life