There was an article in Scientific American a few years ago about the Traveler's Dilemma and how human beings make more money than the Nash Equilibrium tells them to. Edit: Wikipedia summary

It occurred to me that the percentage fallacy might explain why people give high numbers in this version -- the Nash equilibrium is pocket change compared to the max payoff. The same is true for the reward for undercutting; you might not be so motivated to low-ball if your reward for doing so is 2% of the max payoff.

It would be interesting to see an experiment where the payoff for giving the low estimate varied. If you were playing the game with a $10 bonus for lowballing, would you give the Nash equilibrium of $10? Or would you maybe go for the $40s or $50s hoping the other person would go even higher? My guess would be that as the reward for undercutting as a percentage of the max reward increases people get more and more vicious, and at some percentage people will default to the Nash equilibrium.