I sold mine (jailbroken untethered) on Kijiji a couple of weeks ago for $220.
From a lot of the responses I got many people do not understand what Jailbreaking is. Many though (incorrectly) that it would give free content from the iTunes store - something like the old cable boxes.
Well, I realize to some that it is not in the brain surgery realm, but quite frankly, after attempting to learn more about this JB lark, I certainly don't wish to be bothered getting down into the nitty-gritty of it all.
I simply have an ATV2 that is now surplus to my needs and if anyone who needs it for Jail-Breaking purposes, $100 would be more than I expected to realise as well as being less than what the going rate appears to be to buyers.
I also happen to still have an ATV1, for which I would be willing to accept $200, considering that it has the added feature of a 40GB hard drive to accommodate all the additional TV features that Jail-Breaking apparently provides.
Thank you all for your heads-up, it was certainly appreciated.