Back when I originally started using Amazon it got me in the habit of not checking prices elsewhere because Amazon was usually the cheapest, and that was also before I started having to pay my states sales tax. Nowadays, I find the prices are generally not very good, not to mention all the other issues Amazon has, so I do compare prices with other sites before making any purchases. However, I imagine a lot of customers never broke their habit of just purchasing without checking elsewhere which has likely contributed to this.