Your model is too simplistic here. The actual cash leaving Amazon's bank account may not be due to their supplier until 30 or 60 days after delivery. If it takes Amazon 6 days to sell that $100 worth of goods, they can effectively sell $1000 worth of product before that initial cash is due to the supplier if we're talking net 60.
This is how a $100 initial cash investment in inventory can produce $17 worth of cash at the end. You use your leverage with lots of small suppliers to force them into offering generous credit.
Note: this ignores the fact that these numbers are based on net profit instead of gross profit which would be the actual relevant number here. And the gross profit in groceries is a lot higher than 1.7%.
This is how a $100 initial cash investment in inventory can produce $17 worth of cash at the end. You use your leverage with lots of small suppliers to force them into offering generous credit.
Note: this ignores the fact that these numbers are based on net profit instead of gross profit which would be the actual relevant number here. And the gross profit in groceries is a lot higher than 1.7%.