Endowment effects? : "Even" with half a million on the table!

In the television show Deal or No Deal a contestant is endowed with a sealed box containing a monetary prize between one cent and half a million euros. In the course of the show the contestant is offered to exchange her box for another sealed box with the same distribution of possible monetary prizes inside. This offers a unique natural experiment for studying endowment effects under high monetary incentives. We find only weak endowment effects when contestants exchange their box for another box with the same distribution of possible prizes