My home cluster is built from surplus Dell Optiplex desktops that I got from BYU Surplus and added some RAM (before RAM price went totally bananas) and SSDs to.
I spent less than the cost of one of these Pis to acquire all of them together.
I later added a large machine that I used to use as a Linux desktop, with a GPU and 64GB RAM, which I use for generating OpenStreetMap tiles.
I later added a large machine that I used to use as a Linux desktop, with a GPU and 64GB RAM, which I use for generating OpenStreetMap tiles.