Super-convenient shopping services like Amazon Prime and online grocery services can save you time but they can also discourage comparison shopping and they make it all too easy to waste hundreds of dollars a year. Here are three potential traps! Memberships. Yes, we love Amazon Prime because it’s super-convenient and it comes with lots of extra goodies like streaming videos and music and memberships to Costco and Sam's Club are like Disney Land for bargain shoppers, but memb