Incredible free cash flow levels thanks to two or so decades of investment. They are masters of scale.
[ Free cash flow = Operating cash flow - Capital expenditure ]
They used to be criticised by some Wall St types that their cash flow is blah. But to grow your business and not get overtaken by the next competitor you have to invest in yourself (wisely).
The way they run infrastructure allows them to parachute into a new region and begin operations after several months (Australia/Southeast Asia). Saw it with my own eyes. The choice of products via Prime Now in the UK and overseas is amazing.
Now they are entering India and taking on Flipkart (Walmart):