I've cycled it a few times over the years. It still lasts 1-2 days depending on usage when I have it (a bit better than my 4s). My wife leaves it in her purse for a week or so pretty much only using it for text and a few calls.
I've checked ebay - there's 2 as far as I can tell, one for $100 and one for $500 (selling as is, a "part of history").
People are selling parts for $50-60, so maybe a complete one is worth $500.
I have the dock and a couple of different cases for it, including a Sena leather flip top. That should add a few bucks.