[wiremonger]

Counterfactual is a good term for the scenario you described since it is counter to the actual facts in this situation, which are that Amazon's referral fees are in line with all the other marketplaces and it's the 3rd party sellers who are setting prices, not Amazon.

[AbrahamParangi]

Does it seem relevant that other marketplaces with lower marketshare can't reduce their take-rate to lower consumer costs and gain marketshare because sellers would have to raise their prices a corresponding amount if they want to stay on Amazon?

[wiremonger]

How would another marketplace lowering their referral fee cause sellers to raise their prices? They can either keep the extra margin at the marketplace with the lower fees, or they can reduce their prices at Amazon.