https://www.waveshare.com/product/displays/e-paper/7.8inch-e...
But at a similar price point there is also a 10 inch one with decent resolution and greyscale.
https://www.waveshare.net/wiki/10.3inch_e-Paper_HAT
I have this one running in a picture frame
e-ink prices are wild
And from the discussion you posted, I was probably right about the market state at the moment. Damn, what a shame, another monopolized market without real competition.
"Electrophoretic displays (EPD)"
If you look around you'll find 13.3" panels at less than half that price, i.e. without the "maker markup".
The WaveShare one comes with a Pi HAT (sadly with headers soldered on though so I've had to desolder and resolder other headers to them)
And if you get the voltages even slightly wrong you'll fry the display and maybe a few more ...
https://www.waveshare.com/13.3inch-e-paper-hat.htm