I have used this rack as my standing and sitting desk. One rack adjusted for sitting position and one for standing. I used to stand most of the time. Not as conveniently adjustable as standing desk but it worked for me at $100. http://www.staples.com/Hirsh-Heavy-Duty-Riveted-Boltless-Ste...
I have one of those in my basement! Never thought of using it as a desk. Wouldn't it be awkwardly far from you while you're sitting, since you couldn't slide the chair underneath the work surface?