Bias 6: Endowment Effect

You want to go to the concert of your favorite singer. The price of the tickets is normally €30 but they are sold out. You are willing to pay up to €70 for this ticket because you really want to go to this concert. You find a ticket at this price on the Internet and buy it. The day before the concert, you discover that big fans are willing to pay up to €300 for your ticket. What do you do?

Most people prefer to keep the tickets they bought for €70 even though they could have made €300 by selling it. This is partially due to the endowment effect, the fact that we value more what we have than what we have not.

Reference:
Thinking fast and slow, D.Kahneman