You seem to be greatly confused. Amazon most certainly does not generally operate on a consignment model nor does it avoid paying manufacturers for returned merchandise.
It is true that it may pay suppliers only 90 days later or something, but this doesn't change the fact that they still have to pay suppliers.
I genuinely don't know where you are getting your information from, but it is quite wrong.
And as I said before, the stuff that Amazon sends to landfills, has a little to do with the fact that it has been returned (except for things that are so damaged they cannot be resold), and everything to do with the fact that there is no longer demand for it and they need their warehouse space for products that sell better.
It is true that it may pay suppliers only 90 days later or something, but this doesn't change the fact that they still have to pay suppliers.
I genuinely don't know where you are getting your information from, but it is quite wrong.
And as I said before, the stuff that Amazon sends to landfills, has a little to do with the fact that it has been returned (except for things that are so damaged they cannot be resold), and everything to do with the fact that there is no longer demand for it and they need their warehouse space for products that sell better.