I would love to see some DIY home brew, hard parts-only-kit thing to make a stand up desk. I can see where the price comes from but still there has to be a better (cheaper) way.
Not adjustable so at first I didn't mention it, but this is what I have built. Pardon the mess in the photos :)
I bought a tabletop at Ikea in the as is section, and built a standing-height frame for it out of 2x4 and 1" steel pipe. The bases are made from tee pieces and 6" nipples (should have used 10"). If I were to build this again, I would add another piece of pipe running across to connect the two legs (would require adding two tee pieces and nipples, with shorter leg sections). The legs were too wobbly at the flange joints so I reinforced them with steel angle brackets held to the pipe with screws running through holes I drilled in hose clamps.
Using 1" steel pipe as a building material adds up in cost quickly because of all the connecting pieces. I don't have a total cost on this because the purchases were combined with another, much more complex project.