's (NASDAQ:AMZN) elevated valuation rests partially on the premise that if the company maximizes revenues today, profits and cash flow will follow in the future. In this third installment of a four-part series on Amazon's stock, Fool contributor Asit Sharma examines a specific area commonly cited as a potential profit center for the company: its shipping. Asit reviews the current impact of shipping on Amazon's profit and loss statement as well as one important external factor that will also bear on shipping margin in the coming years.

For more insight into Amazon's valuation, check out part one and part two of this series.

Fool contributor Asit Sharma has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.