Game theory analysis of situations like this usually concludes that you won't get $4999. Because another passenger will undercut you at $4998, and take the pro

Game theory analysis of situations like this usually concludes that you won't get $4999. Because another passenger will undercut you at $4998, and take the profit ($4998 - utility of flying) instead. But, of course, you'll anticipate that, and so undercut them for $4997. And so on, until the price converges to near what its worth to you in the first place. That's what makes it an auction. Its harder to exploit than it first seems. (Of course, such analysis doesn't always hold true in the real world - but I wouldn't expect to make 5k with that sign!)