I talked with a guy from Munich who has a similar product. His one-person units cost € 15,000 though.
I think hostels are the wrong market for that sort of thing, because the interior of a "normal" room costs much less than € 3000 per bed.
There could be a market for these things in airports, though. I´m thinking of people who have a few hours until their connection flight and might want to take a nap.
Another possibility could be at large events, e.g. Hannover´s CeBit - there are just too many people for the few hotels in town. Hundreds of these units could be put into one hall in no time. The things could be moved all around Europe on trucks from one event like that to another.
A weatherproof version could be interesting for campsites.
Hint: you won´t get permission to operate these boxes if they don´t have smoke detectors. Imagine an idiot smoking inside, falling asleep and setting the matress on fire. He would suffocate before anyone notices.