Let's say you mortgage something, take on $250k in debt. You now have $250k in assets. Net is zero. You don't take away the debt payments from your income, since you received something from taking on the debt, and it becomes a net positive over time.
It works similarly with operating leases. But the actual accounting is a tad more complicated, so here's a link:
Equity = Sigma(Free-cash-flow) summed over time. In the case of AMZN, equity is about 43B. 18B of this amount is goodwill(intangible vaporware). That leaves with about 25B real equity. And surprisingly, this 25B matches with FCF over the last 2 years(2017-2018). Which essentially means, cumulative FCF until 2017 was indeed 0. Numbers do seem to support the claim that AMZN was running on 0(averaged over time) FCF. Showing 1B in one quarter, -1B in another. But overall 0.
Whether 0 cumulative FCF means predatory pricing is a different question altogether. I'm not so sure about that. How would visionaries build big things, that need, and money? If AMZN loses it and acts monopolistic, I think people will respond by migrating en-masse. No one likes too much inequality. Jeff should do something about that image.
It works similarly with operating leases. But the actual accounting is a tad more complicated, so here's a link:
https://www.investopedia.com/terms/o/operatinglease.asp