19% vs 0.6% makes the two not really comparable.
Not to say you don't have a point (net profit isn't the only factor), just that your example is weak.
Look at the cash flows from operations. This is a big indicator of whether the core business is profitable. I have not looked at Amazon, but non-cash write-off usually play a significant role in lowering net income.
If you operations are sucking up cash, then the sustainability of the business depends on ability to inject new cash from somewhere else.
To say, net income may not be the best indicator of success for high growth tech companies. They reinvest every dollar to continue to spur growth.