A crypto mining rig your players build from parts they have to find. Slot in graphics cards and power supplies, give it power, and it produces Bitcoin for as long as it keeps running.
What it earns comes down entirely to what's in it. There are 39 graphics cards across a full tier ladder, each with its own output, and 14 power supplies whose efficiency multiplies the whole rig. Parts wear down while it runs and eventually need replacing, so a rig is an ongoing cost rather than a one-off win.
It only mines while switched on and powered, which quietly makes generators and fuel worth fighting over. Everything is set from a single config file, and the free calculator on this site writes it for you.