That makes a $170 board that can also do training look dirt cheap in comparison

If you want to train yet-another-convnet sure, but there could be applications where you want to train directly on a robot with live data, as in interactive learning.

See this paper for an example of interactive RL: https://arxiv.org/abs/1807.00412

or a highly rigged machine, this looks more for fast real time ML inference on the edge