Endowment Effect/Bias

Definition 1

Effect of the apparent overvaluing of a possession, including a relationship. (See Loss Aversion, Inertia and Status Quo Bias.)

Source: Behavioral Science Lab, 2017

Definition 2

This bias occurs when we overvalue something that we own, regardless of its objective market value (Kahneman et al., 1991). It is evident when people become relatively reluctant to part with a good they own for its cash equivalent, or if the amount that people are willing to pay for the good is lower than what they are willing to accept when selling it. Put more simply, people place a greater value on things once they have established ownership. This is especially true for things that wouldn't normally be bought or sold on the market, usually items with symbolic, experiential, or emotional significance.

Source: Behavioral Economics