We tend to place a disproportionately high value on things when we had a part in their making. Norton et al. (2012) showed that the labor we invest into something leads us to significantly overvalue it. A group of participants was asked to assign a price to IKEA furniture they had assembled themselves, while a control group was asked to assign a price on the same pre-assembled furniture. The first group valued the furniture 63% higher on average. The paper details several other experiments (origami, Lego sets...) replicating these results. The authors conclude that labor is a significant driver of valuation, suggesting that "labor alone can be sufficient to induce greater liking for the fruits of one's labor."