system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When people/companies sell books on Amazon for $.01, plus a reasonable amount of S+H, what's their motivation?

Media mail starts at 2.69, but IDK what it actually costs for them - these places seem to charge 3.99 generally. I'm thinking its silly for them to sell books for a penny given that the cost of housing the books, packing, sending them out etc., but I don't know.
gpt
they make money from the shipping.  the .01 listing price is just so that it shows up first as the cheapest option in amazon's listings.  and also if you return the item, you'd only get a refund of .01, you don't get refunded shipping.  so it's also to discourage returns.