Interesting article.
However, I think the big problem for these is safety, particularly if you must share the road with cars, trucks and busses. Even for a very fit driver, 50 km/h seems to be a high speed, which is significantly lower than general road traffic in Australia. Combine that with the extremely low profile... let's just say that the odds of getting caught dead in one of these seem a little high for my comfort.
Now, in cities with excellent bike networks, that wouldn't be such an issue - IF the vehicle actually meets the legal requirements for use on bike paths. I'm not sure whether these would be allowed on the bike network in my city. If I had to guess, I'd say the purely muscle powered ones probably are, but I am honestly unsure about the electric/muscle hybrids.
I don't think I'd pay 8000 euros, but if there is one available for, say, 1000 euros, I think I would be interested. You'd want to have somewhere to keep it locked up and safe, though.