the holder might be nice because its big, if you are reworking a heavy ass board that has a big heatsink on it (i.e. power drive), then the stand might be worth its weight in gold, because it might be difficult to make a nice one that can hold up a heavy big board, but you can make most of it with epoxy and aluminum flat bar, at least the edge holder, with good epoxy and clean aluminum that you sanded and prepared correctly. So long you can drill aligned holes and properly use high strength epoxy or threaded screws its not that hard to make with just a drill press thats not horribly off parallel. You can buy steel pins/rods and use those, I think the key for a nice product though would be to use some kind of brass bushings for the slide assembly, you can drill out pieces of brass and glue them into the bars. The thumbscrew might wanna use a heavy plastic bolt so you don't scratch up your slide rods easily.
Reams, taps, drill press, drills, slide rods, aluminum or steel flat stock, file, polishing compound,wax, thumb screws and brass bushings will get you the PCB clamp assembly down.
The high adjustment seems a bit difficult to do right, if you want it height adjustable on the fly, because using threaded rods or thumbscrews is kind of janky, you would want like a collet that tightens on each axis.. Since there are only 4 small points of contacts you will want collets that screw in, or are brazed on.
If you can use threaded rods for the height adjustment, or can live with thumb screws, I think you can make the mechanical part for like 120$ using quality materials. Or much less.
If you figure out how to get a bunch of the appropritely sized collets for the various rods that would be a much much higher quality product.