AMZN: Is This Upgrade Convincing?

Seeking Alpha Analyst Since 2011
The upgrade on AMZN came from William Blair & Co. Main reason: its competitive pricing and wide assortment.
The question is: will these two factors be strong enough to help AMZN win competition and justify ~60% expected growth rate based on PEG analysis? (see here: http://hotstocks.mygroupmedia.com/PEGAnalysis.aspx?StockSymbol=AMZN&Adjustment=Cash).
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