Good idea
The machines can be used as build and test systems for MacOS specific software. Used correctly and you're not going to get near 6 weeks continual use.
but electricity consumption looks to the most likely reason
Why? I thought most of the big data centres were already mainly running from their own renewable power and storage as, given their size, this is signfiicantly cheaper than buying the power in and reduces the need to hedge. Though, in any case the power draw would have to be significant to affect the price. More likely is that Apple has offered a rebate for bulk buying, perhaps to shift inventory ahead of M2 machines.