It’s more than power supply. Cooling and ventilation becomes a MUCH bigger deal at rack scale, and that costs electricity too.
And datacenters have impact on everything around them. If at the end of the day to result is a few more yachts and jets and, a lot more of miserable humans starving in ruined ecosystems, maybe that’s not the best go-to direction.
Cooling demand is only fractional with respect to the load: cooling 1MW of heat will only cost a few 10's to low 100's of kW, depending on the specifics. 10-20% overhead on cooling is probably a close enough estimate for napkin math.