This is the real reason

I mean you could have a smaller cluster

Pis are only 5W, right? 4 of them should still add up to about as much as a midweight laptop.

This is true. Really annoyed that arm as a hole isn't being utilized like it could be by really anyone but apple. We could be making arm Linux powerhouses that sip power like a mid tier x86 laptop. The worry by some is that there is now way to do this without having every component solderd on, but dell has already made a new open laptop ram slot standard that has almost the same latency as Apple's soldered ram.

Arm is the future, and needs to be treated as such more than it is.