I got one way cheaper than I had expected (like $380 or so?) a few years ago. I should use it standing more often, but it does feel good when I am in that position. The past few years, particularly, I have been spending a lot less time being active (my own fault) so it does make me feel better to even do this little, ha.
Recommendation, get one of those ergonomic pads to stand or your feet will get sore quickly. I got some decent sandals that seem to do the trick and I always wear them when I am standing at the desk, and it has a noticeable effect on minimizing my fatigue.