I'd venture further and claim that it's in Amazon's long-term interest to drive down the perceived brand value of third-party suppliers through its distribution

I'd venture further and claim that it's in Amazon's long-term interest to drive down the perceived brand value of third-party suppliers through its distribution channel. Costs are lowered and the value of Amazon's brand is relatively increased. Similar to stocking own-brand product in a supermarket. This weakens the negotiating position of big name brands.