They did a similar frame called the Joker around 2001/2002. The manufacturer was NJC in Italy. I think the one shown is a little later than that and appears to be quite a large size. They are not a one-off custom but there are not that many around. I guess ideal for tri’s with the ‘anything goes’ (within reason) approach to bikes. You may be looking to upgrade the kit on it if you want to race it though.
Difficult to price but I guess it is one of those oddities that is worth as much as the buyer wants to go for and the seller will take as there is little to benchmark it against. Sorry nothing more practical on the value.
If you get it and do any work on it, be sure to post some pics.
I took one for a ride years ago. The BB was like a noodle and I am pretty sure that it does not have 130mm spacing - this would be indicated by the 8sp DuraAce rear Der of early vintage. It was no light weight either. I would pay $500 or so for it - not much more.