With one single exception, that's MY tactic.

 Gotta add the HDs to new rigs anyway, might as well make them big enough to be useful on BURST (at a SMALL increase in cost).


 84 drives in one machine is incredible - even Backblaze only manages 60 on their current Storage Pod design (though they've moved to at least 4 and might be moving to 6 or 8 TB per drive so their total pod CAPACITY is likely a bit higher than yours).

 32 TB of drive is slightly MORE expensive (at NewEgg pricing on the Seagate Externals) than most GTX 1080 ti cards - which pull in close to $3/day each at this point.
 Tradeoff is the ELECTRIC usage of that 1080ti will be in excess of 160 watts and more likely close to 200 watts to achieve that income level, while the 4 hard drives are eating around 50 watts AT PEAK and quite a bit LESS most of the time.


 Up side of those Hitachi (HGST) 2TB is they're likely to last a long time, I'm NOT fond of WD in comparison and I'm VERY not fond of most Seagate models for longevity (I don't have a large data set on Toshiba but the set I DO have has been quite negative, close to Seagate low levels).