"Handling paper" in my note meant how to process, dry to dry. He ended up with a two-roller contraption with the paper in a loop around them. Think of it as a conveyer belt where the print is the belt. This hung into a home-made tray of chemistry. Four trays, dev stop fix & wash. Dump the wash a couple of times. Easy to visualize, difficult to make work in practice.
As far as cost, I haven't a clue. The easel alone took 2 or 3 4x8 sheets of 3/4" MDF. The negative is held in place by taping to a piece of glass, so any format up to at least 10"x10" is workable.
I don't think he is interested in making these for people, or sharing the design for that matter. I just thought this group would appreciate his efforts, and results. Maybe it will gently nudge some individual who has thought of doing the same... the results are incredible. My recommendation for anyone interested would be to realistically decide on your strenths & weaknesses for a construction project like this, figure out which parts will be the absolute toughest to accomplish, and do them first. I would suggest the light source. Stable (both with voltage and temperature), uniform over a 10" square diffuser, with green & blue sources that are individually controlled. Oh, and bright (think in hundreds and hundreds of LEDs). Makes a Durst 138 look like a bargain. I have seen old horizontal enlargers from graphics art shops which would be an excellent starting point, and some of those are available for carting them out.