I've seen them at many retailers in the EU, from Sweden, Norway, Germany, France all the way to Romania, so I'm curious where you're from that you haven't seen any. Ironically, I've never seen them in the US at all during my trips there.

I'm extremely confident that a US retailer using eink price tags would quickly find all their tags stolen or broken and then go back to paper.

Why stolen? You can't do anything with them as it's all proprietary non standard tech.

Other, less scrupulous retailers will buy them.

I doubt it. Those electronic shelf labels (ESLs) are PIN protected for the pairing process. If you steal them from another store you can't pair them to your ESL network if they've already been paired before.

You'd need the PUK from the manufacturer based on the device S/N to unlock them first, but the S/N of each device is tied to the store that bought it so the manufacturer will know it doesn't belong to you and not give you the unlock PUK.

Plus, at the kinds of volumes retailers are buying ESLs, I doubt they'd go through all this trouble to pair a few stolen units.

I’ve certainly seen some combination of eInk and paper, but never a 100% eInk.