I think $240 for the soundtrack poster is pretty nuts...
But this poster wasn't folded... thousands and thousands still exist folded and it can be bought for say $20 - $30 in near mint folded condition with a little effort, but rolled is a different story.
Maybe a few rolled copies went to record stores to pin up, maybe a few to people in the business at the time? But this title in near-mint rolled condition 36 years on is very rare and near impossible to find.
Also, I think the reason it went for such a good price is because unlike a movie poster the folds in this title really spoil it. It's a painting by John Berkey
http://www.johnberkey.com/, it is 100% art, as opposed to a movie poster which is art/ad. (Berkey also illustrated the second edition of the Star Wars novelization.)
You wouldn't want a folded art print. So to find a copy in this condition makes it special. $240... bargain! (I know, next week one will go for $35 but what the hell, I'm sticking to my argument!)
And as for the $20,500 triple bill in the same auction... not a bargain but very nice if you've got the cash