Always take those "I turned down a million" stories with a big grain of salt. It is funny how often those kind of buyers completely evaporate when they have the same opportunity to buy those items at an auction that requires cash payments.
It is an old trick to constantly say "I could have sold this for X" (some skyhigh number) so that when that item is actually offered, half of X looks like a bargain. Look how it worked on that Bride poster. It was offered for over a million dollars on eBay for so long that it started to seem like "the price", and you guys were thinking $700,000 was totally reasonable, and some of you even thought there was a "real" $575,000 bid.
There have only been a handful of posters that sold for hundreds of thousands of dollars, and many of them have been under somewhat dubious circumstances.
This hobby has a TON of "rooters", but very few people with serious cold hard cash. Try offering any of the 9 posters above for sale to dealers at half those prices, and see if you get any takers.
Bruce