yeah, I try not to buy cheap heaters.
mind you, I’ve suggested turning a four by 6"x48" rack into a water heater by adding four of these…
https://www.glaciertanks.com/elemt-r18kw-208-delta-high.html
(you can certainly build much saner devices using parts available at glacier)
EDIT: best answer: @Soxhlet for the win