I remember seeing your advert for it on another website and raising an eyebrow at home much you wanted for it (even with the Motherboard.... )
It was just asking price, people can always talk it down Anyways you can now find it on ebay 400$, I saw one go a month back for over 400£ so plz don't be talking "it is too much" Also motherboard regular price is 150€. (You may look on ebay for example, there it is over 150€)
What isn't sold on eBay is probably what its not worth look at some ended listings and thats generally what it will be worth.
Hmm where did you find it sell for that much? I could happily sell you a complete kit for 300 euros and make a nice profit... I did see one that sold for 60 pounds recently However around 150 euros for the motherboard is about right.