The fact that a business can't sell to a large proportion of households if it's not on Amazon gives Amazon near-total power over that business. Amazon uses that power to demand discounts and charge junk fees to the businesses that rely on it. This allows it to lower prices, which brings in more customers, which means that even more businesses have to do business with Amazon to stay afloat:
https://vimeo.com/739486256/00a0a7379a
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