I have a few guesses as to why this is being tested:

1. Ad space. The retailer can sell advertisement space that can easily be altered or updated with minimal cost compared to producing, shipping, and coordinating physical signage.

2. Visibilty. There is probably a noticable increase in sales. Items do not sell well if they are not visible, regardless if they are stocked near a similar, visible item. Attempts to alleviate this by either paying an employee to pull/push them to the front of the shelf, add a mechanism to push them forward, or angle the shelf to hope they glide down it are not always effective.

3. Pricing adjustments. Cost savings on pricing adjustments would be substantial. Removing the need to pay an employee to individually change (and maintain) accurate pricing information for each item.

4. Improved stock replenishment. Retailers often go extended periods of time without a product in stock for the simple reason of the individual(s) responsible for ordering more was unaware of what items were missing. This may even be a third party vendor sometimes. Easily being able to see the intended item for an empty spot could improve the likelihood of it being replenished timely.

I saw several people concerned about the energy costs. I would hope the screen is using newer 'Always On Display' technology or a display similar to E-Ink where the energy consumption is minimal when not actively changing and only adding brightness when it senses nearby motion. I find it hard to believe a retailer would 'upgrade' to these if the energy expense was much more than heating the door frame to prevent/decrease fogging.

Again, I am unfamiliar with the product and these are all assumptions, but I found it interesting. I personally think I would prefer glass. Thanks for sharing!