I imagine such a thing would draw at least 200W? And pi's maybe 5 watts? So in theory, 30 - 40 pis vs a single server?
The pis also have an advantage in terms of redundancy. A single pi going down shouldn't be a problem and very easily replaceable.
Would be a really interesting article.
There are situations where the economics slightly favor the Pi, but they're fairly narrow with the current gen.
That being said, I am running a NAS and PiHole on a RPi4B right now and am happy. I am planning on turning an old laptop with busted hinges into a server with a nice housing though. I'm very interested how it's going to pan out :)
Edit: I had a 1U server with 2x intel CPUs (16 threads all in all I think?) with 32G RAM in 2012 or so and it didn't see much use. It was LOUD (small screaming fans that pushed air through the chasis) so it didn't see much use.
That’s why I use PIs and custom built a NAS with a supermicro mobo and an i3 (ECC compatible).
The rig the author has is bordering on the ridiculous side and can never match a Xeon, or Xeon cluster.