Google's cash cow product is knowledge of people's behaviors. Can equivalent product be built for much less, or be much easier to use? MS seems eager to build a similar business. Amazon store seems built to survive at a near zero margin. Maybe AWS as well.

I think Amazon's ultimate success is predicated on eventually developing a higher margin business.

It seems many previous businesses founded on the low cost producer strategy, e.g. Dell, uses it as a means to get scale, then emphasise higher margin products and services.