I think you need some basic math. If I buy a book for $10 and sell it for $9.50, I'm not making any profit at all. I'm in the red 50 cents.
Now, if I buy a book for $10 and sell it for $3, and then that guy sells it for $9.50, he makes $6.50, and I'm out $7. At no point does this chain of sales ever get to a net profit, except the first sale, the one the publisher profited from. So where's the money? Why should the publisher be mad? I'm the one who should be mad, because apparently I could've lost 50 cents instead of $7.00.
Also, the book scenario you described, where 10 people read one purchased book, has a name. It's called a library.