So Amazon has a "shopping cart" into which people can "put" their possible purchases while they think about it and browse. Kind of like brick-and-mortar stores' shopping carts.
So Amazon offers a wide variety of items, kind of like brick-and-mortar department stores or for a wider selection, one could go to a brick-and-mortar specialty store.
So Amazon puts tantalizing offers on the check-out page, much as brick-and-mortar stores put impulse-buy items at check-out stands and featured/impulse items on end caps leading to the check-out area.
Amazon is not doing anything unique in any of the things MM highlighted. Everything he cited is an analog of something brick-and-mortar stores have been doing for decades.
And pretty much every online "store" does similar things. Even in registering for a trail or street run the registrant will be offered cancellation insurance, extra T-shirts, a chance to do a gift registration, etc..
Amazon has warehousing and transportation costs to warehouses like any retail business. I think Amazon's big competitive advantages are:
* Not having the expense of the brick-and-mortar outlets;
* Distribution direct to customers, "free", via the taxpayer subsidized USPS or faster and customer-paid instead of the cost of trucking goods to the brick-and-mortar stores plus the cost of selling the goods.
What Amazon does NOT offer is the ability to examine or try on goods, nor service by a knowledgeable flesh-and-blood human being.