[lodi90]

There wasn’t anything unique about Amazon when they started out. There were at least 4-5 other big online only booksellers.

They didn’t really take off until they allowed third party sellers to sell directly to consumers. First media sellers and then other categories. Then amazon used their sales data to cut out the 3P sellers and made even more money selling their own products to amazon customers. The rest is history.

[DoodleBob]

Well-said. It's hard to remember, but if you look at Amazon's 10-K for Fiscal 2018 and Fiscal 2020 you'll see that Amazon lost money in 2014! They went into the black in 2015 and hit net income of $2,371MM in 2016...but a good bit of that was from AWS (more on AWS later). The acquisition of Whole Foods in 2017 helped grow revenue but Whole Foods expanded the reach of Amazon (net income for WF wasn't great shakes when it was publicly-traded).

Things really took off in 2018, when net income leaped from $3,033MM to $10,073MM on the strength of (as you noted) third-party service revenue growth of about $11bn, followed by subscription service revenue growth of $4.4bn. That helped North American operating income explode from $2.8bn to $7.3bn.

It must be acknowledged, however, how important AWS is to Amazon's bottom line. While the operating profit for North America and AWS were almost equal in 2018, by 2020 AWS's operating income was 56% higher than that from North America.

I wouldn't be surprised if Amazon's book selling business was a loss-leader nowadays.