You can buy these at around the same price or less, so no point in doing that

None of them required many cloud specifically, but you have to provide it with STT and TTS engines. You can use other 3rd party or run it on your own hardware, but to do it effectively (have it transcribe your voice in a second instead of 20) you need a GPU.

I am using a few of self-built assistants using https://github.com/formatBCE/Koala-Satellite/tree/main - which was heavily inspired and uses a lot of very similar hardware to HA Voice. I have to say my speakers turned out pretty great.