Good point. As a counter, this article (It's a national review article, so take it with a large grain of salt - I don't agree with it entirely but you and I have likely read the same articles on the other side of this and the NR article provides a good alternate perspective) suggests that the Quidsi case is not really predatory pricing (as the FTC determined in their investigation) as this did not drive amazon to achieve a monopoly in diaper sales (most diapers are still bought in grocery stores etc), even in the online space did not have a long term effect (The founders of Quidsi did quite well for themselves in their next venture, Jet.com). The allegations of undercutting to kill quidsi also came primarily from the founders and hasn't really been backed up. In the long term, that didn't really impact the consumer at all, even if amazon did kill Quidsi, they weren't able to shape the market.
https://www.nationalreview.com/corner/misplaced-trust-antitr...