The first element is sales tax. That means that your chances are only one in 50 that you will pay sales tax on Internet purchases. Unless you live in one of the few states that have no sales tax, you'll receive a substantial sales tax benefit on your Internet purchase. Drive down to the mall and they will never forget to tack on the sales tax. The second element to consider is the value of your time.
Internet shopping covers so much ground in so little time.
You're always seconds away from the next product, or even next store. If you're in a shopping mall like Yahoo Shopping or AOL Shopping, you can jump from store to store in a click. A visit to the mall is a somewhat different experience. I won't debate the fact that a mall has a certain ambience. Some people just love it.