Well, I supose it's like the US Postal Service. Yesterday I went to mail a package in a big brown envelope I purchased at Walmart. The big brown envelope would cost me $9.60 to mail. The lady working the counter at the PO handed me one of their free priority envelopes and nicely told me if I placed the big brown envelope inside the free priority envelope and re-addressed the package I would save over $4.00. Now, how do you explain this works?