The supposed "source" referenced another study (sans link), so I can't get the answer to the obvious question: Was "less expensive" computed using the marginal cost to the customer of this particular purchase? Meaning, do other sites offer the widget for a few dollars less but charge a lot for 2nd day shipping?
I'm a Prime customer, and I've mostly given up on comparison shopping for small items. Amazon's prices are usually good enough that, especially coupled with the free 2nd day shipping, my effective "wage" for comparison is too low to make it worth it. Nevermind the "it just works" feature of Amazon's system (not just website -- the entire process by which a widget comes to my house).
My wife and I have forced ourselves to change our shopping behaviors and ask ourselves before thinking about leaving the house, "Do I really need this thing now, or can it wait a day?" $4 for overnight shipping is a bargain compared to wasted time, gas, etc. Stores are harder and harder to justify. That my wife finds ordering a bunch of clothing, trying stuff on at home, and returning what she doesn't want to be much more efficient makes me wonder what the future of retail clothing becomes. She sometimes even regards the "home try-on" process as superior because she can see how a new item of clothing looks with other, previously purchased garments.