A single TPUv2 host has 8 TPU cores with 64GB of total HBM (8GB per core), but like GPUs, TPUs can't directly access a network, so the host also needs CPUs and standard RAM to send data to them. They are fast, and the host has to be fast enough to keep them fed with data, so the host is pretty beefy. But FWIW, a TPUv2 host has somewhere around 330GB of RAM, not 1.4TB.
There's nothing super-special about the host. The accelerators are the special part (and, as described elsewhere, they are orders of magnitude more powerful than the Edge TPU). However, if you're an academic/independent researcher, being able to access a system with that much system memory/CPU cores for free through TPU Research Cloud is potentially appealing even without the accelerators.
