I have this 5489 Ultimate LEGO Vehicle Building Set, NISB, it not for sale anywhere in Europe as far as I can see. No one on BL has a new one, only 5 used. It is not for sale on BO. I cannot find it on internet as new. Ebay only has used sets. So it seems I have this very rare NISB set, but cannot find the current market value for it. I guess it is what someone wants to pay for it. But how do I price this thing? Also, even if I have the only NISB in Europe, if there is no demand its worth zero. LOL. 

Thoughts? 

I would start with the part-out value here: https://www.bricklink.com/catalogPG.asp

For the settings I tested, the part out value is ~$86 US which is quite high for a basic set.  You can then adjust +/- 15% depending on how fast you want it to move.  If it doesn't sell in 3-6 months, re-evaluate then.  The high part out value is probably driven by a few rare parts.  If the set itself doesn't sell, you can try to sell those parts individually.

List it very high (buy it now listing) then slowly drop the price every week or two. This is assuming you’re not in a hurry to sell it. 

Thanks guys, I've put it up for 125 euro, lets see how it goes. Not in a hurry.