My reference point is physical paper.

You think e-ink has worst contrast than physical paper? How so?

I hold them side by side.

what's the contrast of physical paper in the dark?

We are talking about e-ink without added edge lighting. I found that if I have to crank up the internal lighting of an e-reader to get adequate contrast, then I may as well use a tablet, because it isn’t reflective illumination anymore to the eye.