ROI calc isn't going to net out, but still worth it from a fun/learning perspective.

Used100Th/s S19j Pro from @Kaboomracks: $823 (divide by 3)
Loki Duo + S9 psu: $50 combo promotion from pivotalpleb.com
Vonets wifi dongle: $26
6" inline fan: $30
10"x3.5"x6" fan duct: $12
SC6-6 crimp lugs to mod S9 cables: $10
16 gauge psu cable: had one lying around
14 gauge power strip: same
Lots of duct tape