system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do Amazon used booksellers stay in business selling many books for $0.01?

I understand that sellers have to play by Amazon's rules or be undersold. Do they make a small margin on handling? Are these free book stores staffed by volunteers? I'm trying to decide whether I'm taking advantage of someone by getting text books this cheap.
gpt
I managed an online book company for the past 4 years. It's the shipping. Amazon sets the shipping charge for all books and media at 3.99 (USD). Most of those books are going to cost me around .80 (possibly less) to ship anywhere in the US, .08 for materials, labor is pretty small, on the order of fractions of a cent for any one book. We list around 1200 books a day, and ship around 2000-2500 a week. Pretty much, it's volume (which also gets you the shipping discounts for being a bulk mailer), and cheap shipping.