The Betty Crocker Effect

The Betty Crocker effect refers to how, in the world of instant cake mixes, when something is too easy it reduces the value. The legend goes that instant cake mixtures that just needed water didn't sell nearly as well as when you needed to add an egg. Adding the egg yourself gives investment in the process of making the cake so we appreciate it more, and the extra effort demonstrates the act of love that is baking a cake.

Also easy to understand as the IKEA effect. As is so often the case, Dan Ariely explains it well. 20mins well spent watching Dan Ariely's TED talk What makes us feel good about our work?. You can jump straight to it around 12mins 50s.