How much an item is "worth" I have always felt, is directly proportionate to how much one is willing to pay for it. If someone prices a figure at $200, that originally sold for $50, I always feel that its been overpriced. A great example of this is the Hot Toys figures, and not just the POTA ones. They come out at a higher price and then sore to the heavens in the secondary market. Now, while some of those may be worth a bit extra because of better bodies and sculpts, etc... I've NEVER felt that the deep markups on Sideshow, BBi or Dragon figures were ever worth it.
Take Dragon's Star Trek:TNG figures that came out last year. Way overpriced at their SRP [$125 iirc] but a nice pickup at $27.
All that being said, if it were me, I would start it at $100, with free shipping and a reserve of say $300. That way if it doesn't get as high as you'd like, you have an "out" to keep it and try again in a different way or to offer it to a high bidder.