[zamadatix]

To be clear this isn't an alternative to hosting a single Pi it was in response to the distributed case:

> Maybe there are ARM-specialized, highly distributed tasks for which a fleet of Pis is particularly efficient?

Assuming the task really requires ARM, is perfectly scalable among multiple systems, doesn't require more than 10mbps between the nodes, and doesn't require dedicated control/scheduling nodes (i.e. best case for the Pi's) a fleet in multiples of 10 Pi's per would be $59.90 month each plus the up front cost of the Pi's, power adapters, SSDs, and shipping. And even if you wrote off the up front hardware as on hand it would still be significantly less green to run.