You know, a couple of days ago there was an article posted here regarding the high cost of gasoline. The aithor of that article broke down the actual cost of each gallon of gas. In that exercise he noted that it cost $0.11 to deliver each gallon of gas to every corner gas station. The author then compared that $0.11 cost of transportaing each 6.6 pounds of highly flammable gallon to the $0.47 required by the post office to deliver a feather-light piece of paper. Very effective contrast indeed.
Obviously, cost of a stamp is $0.39 not $0.47 - yet.