Not to mention that Amazon drivers are delivering to dozens of stops along their route to you, making them far more efficient compared to each consumer traveling to the store in their own vehicles.
Yeah that too, although I'm not looking to throw my weight behind that argument as I've seen how many redundant deliveries Amazon tends to make. Never mind the amount of stuff one has to return due to it arriving broken or due to trying to mitigate their customer-hostile policies. I'd like to think this demonstrates how cheap amortized delivery actually is, but I think the truth is they've just got things set up so sellers eat the costs.