The chargeback model does not operate the way you are describing.
Yes, major retailers have various agreements with manufacturers. Sometimes it's return-to-vendor, because the manufacturer wants the returned items back in order to refurbish and resell itself, etc. Sometimes there are return allowances, such as a 3% rate, meant to cover an expected return rate regardless of return reason, or they negotiate with Amazon for it to determine which returns are genuinely defective, and then those and only those get effectively reimbursed.
But it is completely false to say that Amazon is generally able to pass on the cost of all its returns to manufacturers, that this makes returns zero-cost for Amazon, and that it therefore just tosses returns in landfills. That's not how anything works. Neither manufacturers nor Amazon have any kind of financial incentive to just dump returned merchandise that can still be profitably resold.
Yes, major retailers have various agreements with manufacturers. Sometimes it's return-to-vendor, because the manufacturer wants the returned items back in order to refurbish and resell itself, etc. Sometimes there are return allowances, such as a 3% rate, meant to cover an expected return rate regardless of return reason, or they negotiate with Amazon for it to determine which returns are genuinely defective, and then those and only those get effectively reimbursed.
But it is completely false to say that Amazon is generally able to pass on the cost of all its returns to manufacturers, that this makes returns zero-cost for Amazon, and that it therefore just tosses returns in landfills. That's not how anything works. Neither manufacturers nor Amazon have any kind of financial incentive to just dump returned merchandise that can still be profitably resold.