The current standard is "consumer harm" with lower prices considered per-se evidence to the contrary. The issue here is monopsony rather than monopoly because A

The current standard is "consumer harm" with lower prices considered per-se evidence to the contrary. The issue here is monopsony rather than monopoly because Amazon is fantastic for consumers but Terrible for sellers because there is effectively a single online market to sell in owned by Amazon. My worry would be a feedback loop giving Amazon increasing dominance due to this effect, and would like to see both vertical integration and Monopsony more heavily scrutinized, but this lawsuit seems to target a feature with an objective benefit to consumers given Amazon's amazing shipping and return policy.