What I think is strange with stuff like this that you should be able to come to that conclusion without technical knowledge. Just the fact that everyone runs AI on GPUs and NVIDIAs stock skyrocketed since the AI boom should tell you s.th..

Did OP really think his fellow humans are that moronic that they just didn't find out you can plug in together a cuple of rasperri pis?

Nobody thought an RPI cluster would ever be competitive, and Geerling never expected anybody would. But it's fun to play "what if" and then make the thing just to see how it stacks up and that's his job. Any implication or suggestion of this being a good idea is just part of the story telling.