If you ask me, mac2sell is overinflating prices by about 30-40%.
It doesn't consider how old the macbook is.
ex. $720 for white MB, C2D, 4GB ram, 320GB HD.
For this price I'd buy a new refurb any day of the year.
Realistically, the mac i listed above is worth no more than $600.00, with nvidia 9400m graphics (anything older would be a lot less, something mac2sell does not consider).
If you want to find out true value of your laptop, look at ebay's completed auction listing, for auctions where winning bidder has a lot of positive feedback. All the bids that you'll see in the $800.00 range for a Macbook were scams, where the bidder is trying to get the item shipped to some country that most people wouldn't know exists.