Some of the problems people have when it comes to Amazons financials, or any other companies at that, is the (in)ability to differenciate between cash flow (Amazon retail) and profits (AWS, marketplace and FBA).
Once you grasp that, all of things make a lot more sense.
Indeed, I forgot to put that up there. The big difference between Retail and AWS is that Retail has obviously expensive ways to grow. And has to have an absurd float in the form of inventory to work. I think datacenters have a bit of that, as well. But I would be shocked if it was to the same level. AWS, on the other hand, seems to genuinely have trouble finding ways to spend all of the margin they pull in.
Once you grasp that, all of things make a lot more sense.