This paper explores a possible connection between two behavioral anomalies in economics, the observed responsiveness of individual decision-makers to sunk costs, and the apparent failure of backward induction to predict outcomes in experimental bargaining games. In particular, we show that under some conditions, a "sunk cost sensitive" fairness norm can evolve in such environments. Under this norm, a fair distribution allows all parties to recoup whatever each has invested in their relationship before the net surplus is then divided into equal shares. The establishment of such a norm would have important consequences for the hold-up problem, which we characterize in terms of ultimatum bargaining in the presence of an outside option. We then conclude with a brief discussion of the possible labor market implications of our results.