Everything is worth what its purchaser is willing to pay for it
I feel this gadget falls into the category you have so marked. It is not directed at a specific need (that I am aware of) but is an expensive toy to me because it is not in my budget range and does not offer a feature that I would need over my existing phone.
However, I feel that you are incorrect in making the statement "so much for so little" without context. The use of "so little" is subjective without any qualifications. Someone may find that the increased screen size is worth every penny spent. This is because their qualifications are different from yours. I dislike the idea, particularly on a tech site, that it is too expensive or doesn't meet the need when neither have been defined as a qualification. It is merely something on offering and it would appear that it is not targeted as a device for everyone but a "premium" device. It is fine to make a prediction like "I don't expect this to sell well because its cost is high compared with most phones in the general population" as that is including a qualification to demonstrate why you have your point of view. Nothing wrong with having one but just making a broad statement without backing it up does not contribute much to the discussion. It is these types of devices that can open up new use cases or demonstrate an idea that needs maturing. I often hear the complaint that I wish my screen were bigger when the people around me are using their smartphones. While finger gestures allow in some cases to easily magnify something it may simply be too troublesome to use on a larger document or picture (such as a comic). Using a different device with a larger screen size may not be so practical as the smartphone is so portable and readily available because it goes everywhere with you. This is an attempt to try something different though it is not clear if it solves the problem. Cost, more room for screen clutter such as in app Ads, device longevity, and battery life are all valid concerns. It might not do the job. However you can't say for certain without trying. The attempt alone can yield value in the form of knowledge gained.