I don't know exactly what US anti-trust law says, but German anti-trust law also considers what kind of power you have over competitors and suppliers to decide whether you're behaving anti-competitively. We call it (roughly translated) "Law against constraint of competition". Amazon might qualify as abusing their position under our laws. Unfortunately, it can be difficult to get a case started if the relevant authority isn't paying attention because of how the justice system is structured here and there's a question of how badly companies are actually being impacted in Germany by Amazon's behavior. Our wholesale/retail market seems to be a bit different and far more diverse than in the US.