Just pulled up their filings[1], and I'm almost certainly misreading it, but in Q3 2017:

  NA Retail Revenue: $25,446M
  NA Retail Profit:  $   112M
  AWS Revenue:       $ 4,584M
  AWS Profit:        $ 1,171M

Pedantically, it seems like AWS is not Amazon's primary source of revenue, but is the primary source of profit.

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[1] https://www.sec.gov/Archives/edgar/data/1018724/000101872417...