As someone who has done some, (well lots actually,) buying on ebay, my gut feeling is that this is a genuine sale and I think he could have asked a bit more for it. Ok, it's illegal and the regular, legal Kalkhoffs are more than adequate so perhaps therein lies the reason for the very decent price.
The MPG will be rubbish compared to their legal bikes with that big battery and most discerning ebikers seem to want more than this machine could ever provide, judging by the kind of posts I have read on this forum.
I can well understand the vendor's stance with regard to the questions he's been asked but no-one is going to be forced to buy the bike should it turn out to be something other than the advert describes. I would have no hesitation in bidding for this bike but it's pointless. A regular Kalkhoff makes much more sense and there are no niggling concerns at the back of the mind if something goes wrong causing the authorities to look closely.
Indalo