Fair call regarding the inline fan. The Health Pro Plus is a bit cheaper than the GC Multigas, I emailed an Australian seller of these units to ask a few questions. The units seem well priced compared to many that a crazy expensive as you said ($6-$12k)!
This might not be the best setup in the world, but I ran the machine without the filter or the inline fan and it was headache central. Once I got the inline fan the headaches stopped and the smells ended for me. Every now and then I might get a whiff but compared to nothing it is night and day difference. The filter was just to make sure that nothing was left behind that the inline fan missed. I imagine a total room scrubber is probably better but I run my shop out of a room in my home. If I had a professional shop it would be a completely different thing. I would have the printer in its own closed off room with a scrubber in there so I wasn't even around it.