The DGX-2 is the fastest AI computer on the market right now and can be also seen as the largest GPU in the world, thanks to the new NVSwitch system that interconnects 16 GPUs. It costs $399K, but it can easily replace US$3 million worth of 300 dual-CPU servers consuming 180 kilowatts. This is 1/8th the cost, 1/60th of the space, 18th the power.
https://www.notebookcheck.net/Nvidia-DGX-2-is-the-world-s-largest-GPU.292930.0.html