I think I paid $700 including shipping from Japan for mine (in 2004). At the time I'd never seen one other than in the old promo material so I wasn't as concerned with price, but the four or five I've seen since usually sold in that 700-1000 range. Every II I've seen was made in the mid to late 70's. They're definitely worth more than the IVs that came later. What's weird is I've rarely seen a IV from the mid 70's, they're almost always mid to late 80's.
I don't know that these basses fit in an easily predicted price range like a typical mass produced bass would. They're rare enough (but limited enough in their appeal) that the only real factor in price is how bad the seller needs the money and how much the buyer wants it.