300-400 because remember when retailers have holiday sales the list price of 500 can go down to 400 brand new. Based on that and what you can get on ebay for them used, I think a fair price would be 350 including shipping.

My trick to estimate value is to search for the item on eBay then change to advanced search and check the box to search the the completed listings.  This gives you a clear range of what people are actually willing to pay for the item at autction.  A direct sale may be worth a little more.