Samsung's DeX dock is now available for $79.99 in the US straight from the Korean maker's website - $70 off its original MSRP. Meanwhile, Amazon will sell you one for $82.99.
It's the old version of the dock, the one introduced with the Galaxy S8 (but will work just as fine with the new S9 and S9+), that keeps your phone upright. The new dock, on the other hand, lets you use the phone as touchpad potentially saving you from carrying a mouse.
DeX v.2 (a.k.a. DeX Pad) is available on Samsung's website for $99.99, so it only made sense for the old version to get a discount.