Why Do Things Feel More Valuable Once We Own Them?

You might pay no more than $20 for a mug before owning it, yet feel that selling it for less than $35 is not worthwhile moments after it becomes yours. This tendency for the price demanded to give up an item to exceed the price offered to acquire it merely because it has entered the category of “mine” is often called the endowment effect.

In a 1990 experiment, Kahneman, Knetsch and Thaler randomly gave mugs to some participants, then asked owners to state selling prices and non-owners to state buying prices. Fewer trades occurred than a traditional model predicted, and owners demanded substantially more. A classic explanation treats ownership as a reference point: acquisition is a gain, while selling is experienced as a loss, and losses often carry more weight than equivalent gains.

This is not the same as a sunk cost. A sunk cost is past time or money continuing to shape a future decision. The endowment effect can appear even when an object has just been received for free, before long attachment or investment has formed. Nor has the mug objectively increased in value; the buyer and seller face the same object from different positions.

Still, not every gap between buying and selling prices proves a fixed bias. Budget constraints, misunderstanding of trading rules, opportunity costs, whether the good is for ordinary consumption, and market experience can all change the result. Some studies find a smaller effect when procedures reduce misconceptions. The useful lesson is not to stop valuing our belongings, but to ask when selling, decluttering or changing tools: if I did not already own this, would I buy it today at the same price?

https://www.journals.uchicago.edu/doi/10.1086/261737
https://pmc.ncbi.nlm.nih.gov/articles/PMC7983076/