Endowment effect
Etymology
From endow, via Latin dotare, "to provide with a gift." The economist Richard Thaler named the effect in 1980; the classic demonstration by Kahneman, Knetsch, and Thaler gave people a mug, whereupon their asking price leapt above what buyers without one would offer for the same object.
noun · /en-DOW-munt ih-FEKT/
The tendency to value something more once you own it than you would to acquire it in the first place.
What it names
Why we ask more to give a thing up than we’d ever pay to get it — ownership itself inflates the price in our heads.
Example
The endowment effect is a used-car seller’s curse: the car is worth more to them simply because it’s theirs.
Related idea
Loss aversion is the deeper cause — giving up what you have registers as a loss, which stings more than the matching gain.