I highly doubt anyone is going to pay $15k+, or even more then a a few thousand if he's lucky.
While it's definitely a rare poster, possibly the rarest - 18 of the style and 2 of the specific theater are the only ones ever made - it's still a re-release. And a text only one at that. The only people I think would be interested in it are the Star Wars completists. It's also dry mounted, which hurts the value. And the seller listed it as local pickup only, with no shipping option. Maybe he assumes that the only people who can afford his reserve can just jump on their private Gulfstream and fly on up to where he is to pick it up? He listed it on eBay, which probably wasn't the smartest move - assuming he actually does want to sell it. Lastly, there are a few other uber rare SW posters coming up for auction soon. Ones that are almost as rare, but much more desirable.
Personally, I have my doubts whether the seller actually wants to sell it. His listing details/description and unknown "VERY high" reserve almost seems like a ploy to use eBay as a valuation tool, rather then a selling one.