How exactly are author's paid?

When authors sell a book to a publisher, the publisher pays them an advance and an additional royalty which is a small percentage of the book price for every copy sold. While The Last Unicorn did well (and I believe was even made into an animated film...), if the author was roped into signing an unfavorable deal, he might not have made all that much money. It's doubtful the author got more than a few cents per every copy sold. A lot of people are profiting from a printed book, including the author and publisher, but also the cover designer, editor, marketer, distributor, binder, printer, etc. All of these people are receiving a small cut from the book. Also, perhaps the money is slow in coming. After all, the book probably didn't sell 6 million copies over night; those copies were sold over several years and possibly, the sales haven't kept up with the prices of living and inflation.