The NXP® i.MX 8MQuad board is available for 150$ and has USB3 and PCIe. The TPU would probably be attached through one of those buses. I would bet around 250$ with the TPU which is pretty good and puts it around half the Jetson Tx2, 1/5 the Xavier. I wonder if the TPU could be used for SLAM not just object identification, now that would be useful
Plenty of affordable options on the market already. For a hobbyst I would highly recommend to use tegra instead. It is compatible with all frameworks and won’t lock you down on google stack