Maybe too late, but there's no such thing as a fair asking price unless you mean something below fair market value. For instance, $10 would be very, very fair to a buyer.
You can always start at $1, make it a 10 day auction and with a Buy It Now price that you would like to get for it. And what is that, reasonably? Do a search for the 810, click on Advanced, and then select Sold Listings. Scroll through them, and you will start to see a median price range for sales. The top priced items are often new, but not necessarily so, and the bottom tend to be defective phones. You should definitely look at at least half a dozen of the listings at all prices to see what was going on.
Good luck.