I think between a few of our historical setups, we can beat that lot.
We have the Greyhouds, MAOJC, CrunchHog, DT-Loft, Mojos LTSP to name but a few …
17 isn’t trying hard enough 
I only ever managed 13 at one time - an 1+7 device LTSP set up in the garage roof and 4 self built PCs - 2x windoze and 2x Linux in the ‘PC Room’ plus a work laptop = a £1750 a year lekky bill.
Now reduced to Win 7 on a 6 core i7 with a 660ti to crunch on, and an old Q6600 rig that I still mess around with Linux on, and 2 android tablets for browsing, reading etc.