Yea, in this case, there is no 'book value', so it's worth what a given consumer will pay. Since they aren't available in the states, it's not like you could choose between a few for the best deal, or even wait 'till another comes along. For me, although I am cheap, would be willing to pay for something like this, as I have a thing for rare and unique items. When I was in high school, I considered a '72 Lotus Europa...
As far as parts go, I'm sure many from the older XT600 dual sport will fit, the problem would be finding which ones. Other parts may have to be ordered elsewhere (like Europe, they are very popular there). I don't think I'd use it as my daily driver....