I purchased this desk (Amazon.com) for $286 (with a Prime membership).
I wanted to get a relatively inexpensive standing desk to see how I'd like it. I've been using the desk for two months now and love it. I'm sure it doesn't have all the adjustments more expensive desks have but I feel very comfortable working all day.
It took almost two weeks to adjust to standing all day long, but now I cannot imagine not working at a standing desk. I think part of the aforementioned comfort is due to all the movements my body is now making. I do find myself unconsciously stepping back, moving my arms around and other movements that are recommended periodically while sitting all day. I even find myself swaying side to side while I'm thinking through a process and stop as I continue to type away.
The improvement in how my back and shoulders feel is great.