The endowment effect
Researchers have tested this many times, in different places, over many years, and they keep finding the same result. This one is safe to trust.
Researchers gave people a plain coffee mug and then asked, at what price would you sell it? On average, the owners wanted about seven dollars. Then they took a separate group who did not have a mug and asked, what would you pay to buy one? That group offered about three dollars. Same mug. The only difference was who happened to be holding it. Simply owning the thing, for a matter of minutes, roughly doubled or tripled what people thought it was worth. Nothing about the mug had changed, no new information, no improvement. Ownership itself inflated the value, and the owners did not feel irrational, they felt the buyers were lowballing them.
Anything you own, or made, or authored, feels more valuable to you than it does to anyone else, and the feeling is invisible from the inside. This reaches far beyond mugs, into your hiring brief, your plan, your draft, the strategy you built. You defend it partly because it is good and partly just because it is yours, and you cannot easily tell those two apart. When you find yourself unable to understand why others do not see the value in something you created, remember the mug. Some of that gap is the work. Some of it is only ownership. When you also built the thing yourself, the effect is larger again, which is the IKEA effect.
The endowment effect says owning a mug triples what you think it is worth, and the premium is invisible from the inside. Loss aversion says losing hurts more than an equal gain feels good. The endowment effect holds; loss aversion is still argued over. That is an odd shape, because loss aversion is the usual explanation given for why ownership inflates value: selling feels like a loss and buying feels like a gain. So the effect is solid and its explanation is contested. What that leaves you with is the effect on its own terms. You will defend what you authored partly because it is good and partly because it is yours, whatever the mechanism turns out to be, and the mechanism being uncertain does not make the premium any smaller.
Source: Kahneman, Knetsch and Thaler, 1990, Journal of Political Economy.
Dan Ariely, 2008
A tour of the quiet ways ownership, expectation, and framing bend what we think things are worth.
Draw your own card. It does not take long, and it rewards taking your time.