I'm pretty sure you can't buy TPUs, but people usually buy GPUs instead. If you're building a personal rig, these days, you can get an Nvidia RTX 3090 for about $720 USD on ebay used, which is pretty cheap for 24GB VRAM. There's also the A6000 with 48GB VRAM but that'll cost about $5000 on Amazon. Of course, there's new cards that are faster with more VRAM like the 4090 and RTX 6000, but they're also more expensive.

Of course, this is all pretty expensive still. If your models are small enough you can get away with even older GPUs with less VRAM like a GTX 1080 Ti. And then of course there's services like Google Collab and vast.ai where you can rent a TPU or GPU in the cloud.

I'd check out Tim Dettmers' guide for buying GPUs: https://timdettmers.com/2023/01/30/which-gpu-for-deep-learni...

Apple and Google consumer hardware have specialized ML compute features.

https://www.tomsguide.com/news/google-pixel-7s-most-critical...

https://www.macobserver.com/tips/deep-dive/what-is-apple-neu...

Depending on your definition of affordable, the windows dev kit 2023 makes a big deal out of their NPU but you'll have to deal with windows 11 to access it unfortunately

Qualcomm has an SDK [1] where you can run software on a DSP/NSP simulator.

[1] https://developer.qualcomm.com/software/hexagon-dsp-sdk