Ikea effect
n. Increased feelings of pride and appreciation for an otherwise cheap or poor-quality object because it has been self-made or self-assembled.
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"The IKEA Effect" is when we buy something and put it together ourselves. We then use it (or hardly use it, whichever), but develop an attachment or sense of pride to this object because of the work it took for it to be completed and rendered usable.
—“Why we D.I.Y. or the "IKEA Effect,” Chicago Now, September 28, 2011
Across four new studies, researchers from Harvard, Duke and Tulane University find that increasing the labour required for a product actually leads to greater appreciation for it….

They refer to this as "The Ikea Effect" — named after the Swedish retailer known for its DIY furniture.
—Misty Harris, “'The Ikea Effect',” Ottawa Citizen, September 19, 2011
2006 (earliest)
One of his experiments involved having people make origami and then compare their creations to those made by someone who excels at origami. What Norton found was that people would wildly overvalue the origami they had made, even if it wasn't very good, because they spent the time making it.

Norton calls it the "Ikea effect" because he's found that shoppers who assemble furniture purchased at the Swedish big box store seem to value the furniture more than it's really worth.
—Bruce Mohl, “What's worth more, your money or your time?,” The Boston Globe, February 26, 2006
More emphasis on ready-to-assemble. Some industry analysts call this "The Ikea effect," after a Swedish retailer that has stores on the East and West coasts. This category, once tagged "knockdown furniture," is cropping up in the most established furniture makers' inventories
—Ellen Neuborne, “The couch indicator,” USA Today, March 04, 1993