i wouldn't have used a cropped photo from the auction page for an estimate thread, especially since 99% of estimate threads aren't estimate threads (people are just looking to hear that whatever they have just purchased is super rare and valuable, and will consider anything below X00$ to be an insult to their intelligence)
just list it for whatever you think it's worth, that's really the only answer, and then lower it at each relisting if nobody bites. make sure the title is as ominous as possible to catch buyers' attention