Google does not sell them, but you can rent them:

https://cloud.google.com/tpu

As you note, they'll set the margins to benefit themselves, but you can still eke out some benefit.

Also, you can buy Edge TPUs, but as the name says these are for edge AI inference and useless for any heavy lifting workloads like training or LLMs.

https://www.amazon.com/Google-Coral-Accelerator-coprocessor-...