This is shocking, troubling, and so obvious. Emphasis mine; I recommend reading the whole article on HBR.
Psychologists Kimberlee Weaver, Stephen Garcia, and Norbert Schwarz recently illustrated the Presenter’s Paradox in an elegant series of studies. For example, they showed that when buyers were presented with an iPod Touch package that contained either an iPod, cover, and one free song download, or just an iPod and cover, they were willing to pay an average of $177 for the package with the download, and $242 for the one without the download. So the addition of the low-value free song download brought down the perceived value of the package by a whopping $65! Perhaps most troubling, when a second set of participants were asked to play the role of marketer and choose which of the two packages they thought would be more attractive to buyers, 92% of them chose the package with the free download...
The same pattern emergences when you are creating deterrents or negative consequences to discourage bad behavior. In another study, participants were asked to choose between two punishments to give for littering: a $750 fine plus two hours of community service, or a $750 fine. 86% of participants felt that the fine plus community service would be the stronger deterrent. But they were wrong — in fact, a separate set of participants rated the $750 with the two hours of community service as significantly less severe than the fine alone. Once again, they reasoned that the overall punishment was on average less awful because two hours of community service isn’t so bad.