>One day someone else will push Amazon out.

The question is, "at what cost in the intervening time?"

We've also not seen the combination of scale, network effects and technological capability that's available to companies like Amazon today, making monopoly power even more potent. It's not 100% clear that the potential for their displacement is remotely as viable as has historically been the case for companies.

The cost is whatever it takes to convince one rich person to decide it's profitable to invest in a competitor.

Not sure if your comment simply stems from a misunderstanding or you intended it as a pithy way of saying that, as consumers bear the cost, investors will see the opportunity to relieve their pain and move to compete.

Either way, though, the problematic piece (and primary rationale for antitrust law) is that it's the consumers who are bearing the cost.