Here’s a fantastic infographic that presents a visualizes the answer to the following question: How Much Do Music Artists Earn Online? If you think those results look abysmal, try publishing a book.
Here’s a book publishing case study to consider. A couple of years ago I worked on a 72-page book. The book features one-color illustrations on the text pages and full-color cover. The cover price is $5.99. It costs $1.58 per copy to have the books printed and delivered to the warehouse. You’re probably thinking that’s not so bad. There’s a $4.41 profit and the author (assuming the author receives a 10% royalty) walks away with $0.44 per copy sold. Not really impressive is it?
The publisher has to ship inventory to booksellers (online or brick-and-mortar) and that costs quite a bit. For example, let’s say the publisher receives an order from Amazon.com and one product is ordered. It costs the publisher $0.97 to properly pack and label the order and $2.13 to mail it using USPS. So far, the publisher costs for one book sold through Amazon.com is $4.68. That reduces the profit margin to $1.31 per copy. Like most retailers, Amazon.com buys books at 55% off the cover price: $2.70. You’ll notice that the publisher is running a deficit. It literally costs the publisher $1.98 to sell a $5.99 book title. The author receives no royalty.
If the publisher sells the book through its own web store, then the net profit is $1.31 for one book sold. The publisher pays the author $0.13 per copy sold.
All that to say, the author of the book in this case study needs to sell 2,240 copies on the publisher’s web store to earn the same amount of money that an employee at Hardee’s (earning minimum wage) earns in a 40-hour week.
Coffeehouse Junkie 
I think your math is off a bit. It shouldn’t cost $2.13 per book to ship it unless you are shipping one book at a time to Amazon. You ship in boxes or pallets and they should pay some of that cost. If an individual orders direct, they pay for shipping.
So once you give Amazon 55% of list price it’s still $2.70. Less the 1.58 to print and deliver, it’s $1.12 gross profit.From which you pay people to ship boxes or pallets of books and hopefully for the writer, 10% goes to them for writing the damned thing. I don’t know what 10% they get their commission derived from.
You are correct. This case-study is based on a single copy shipped to Amazon. Some weeks there are maybe a six books that ship. Other weeks, as many as 70 copies ship to Amazon.
I’ll recheck the numbers and present another post next week.
One thing I should mention is that this case-study is for small, independent publishers not major publishing houses. Would it be helpful if I wrote a post about the economies of book printing?