I stopped reading and started researching there. Amazon has positive cash flow, both overall and from operations specifically, which is what would would matter to this argument.
In the linked-to post, the author states
> In fact, if a careful observer overlooks the GAAP loopholes that allow Amazon to dress up its numbers, during 2017 the firm experienced a negative cash flow of $1.461 billion
This is very wrong. That calculation stems from the section of their 10-K titled _Free Cash Flow Less Finance Lease Principal Repayments and Assets Acquired Under Capital Leases_. As the section says "Free cash flow less finance lease principal repayments and assets acquired under capital leases is free cash flow reduced by “Principal repayments of finance lease obligations,” which is included in cash flow from financing activities, and property and equipment acquired under capital leases. In this measure, property and equipment acquired under capital leases is reflected as if these assets had been purchased with cash, which is not the case as these assets have been leased.", which is to say, it's including both a remix of items that already exist on the cash flow statement, and things that weren't paid in cash but are being treated as if they were.
If Amazon were truly selling below average cost, their operating cash flow would be negative. It's not; it's positive. As is their cash flow from across operating, investing, and financing activities.