I don't know about Amazon, but years ago I read an article about Walmart that made the case that products sold there from the same brand tend to be worse than those available elsewhere. Levi's jeans were an example.
For Walmart, they have scale and a monomaniacal focus on lowest cost. Each time a contract with a vendor is renegotiated, Walmart demands a lower cost, and they're big enough they get it. The predicable effect is the vendors skimp and cut costs on what they send to Walmart because they're under so much pressure, and Walmart doesn't care as long as they get a lower price. That can mean vendors doing stuff like binning by quality, and sending the worst stuff to Walmart; using a special grocery-store shrink ray for Walmart, special Walmart-specific cost-reduced designs; etc.
For Walmart, they have scale and a monomaniacal focus on lowest cost. Each time a contract with a vendor is renegotiated, Walmart demands a lower cost, and they're big enough they get it. The predicable effect is the vendors skimp and cut costs on what they send to Walmart because they're under so much pressure, and Walmart doesn't care as long as they get a lower price. That can mean vendors doing stuff like binning by quality, and sending the worst stuff to Walmart; using a special grocery-store shrink ray for Walmart, special Walmart-specific cost-reduced designs; etc.