WOOD sells the downloadable plans for that cyclone for about $7.00. And from what Ive read, the cost of building it is $50-$100.00. The expensive part is the fan, and you wont find one used unless you are really lucky. Any old furnace fan WONT work. I just built a drop box, and then the budget died. Gotta finish that boat, y'know... I suspect I'll regret not doing a cyclone. But I'll dump outside.

Regarding the shop vac, no comparison, The DC is a lot quieter, and more efficient. It moves higher volumes of air, 600-1000 CFM, at lower pressures, 6" - 10" water column. Most shop vacs are 100 CFM or less, and up to 70 or 80". More for handheld tool extraction.

The air cleaner is a different animal. It is designed to pick up the part that the DC doesnt get, and unless you have a pretty good hood design at each machine some dust will still get in the air. Ultimately, the combination of the two is what is needed. The cleaner is simply a furnace fan and filters. Easily built on the cheap, especially if you can find a free fan.
: Check out past issues of Wood Magazine--maybe up to two years ago. They had
: plans for a home-made cyclone collector that may be more affordable. Good
: luck. Tom