You should pay for the books cause books don't just fall from the sky. Authors invested time and money to publish them, and even if most of them are utter garbage, the realization that you were tricked into buying them with unethical marketing practices, has its value. In other words, you paid for the valuable lesson, for being naive. But if you decide not to pay besides the obvious benefits you gain from using the book(s), you will pay the price sooner or later in some other way, cause the bottom line, we are all "One". So you basically stole from yourself and in that way, you created a certain disbalance in Universe, which will find a way to balance itself one way or another. For example, a few years from now, your car may malfunction in some deserted place, where the price for fixing it will be 10x larger than usual, and you will have no choice but to pay for it. Is that curse of the author catching up with you for stealing his or her book? Of course not! That is stupid cause sending the curse to hundreds or thousands of potential "book thieves" is a suicidal act. Every curse no matter how justified may seem at the time of launching, has its blowback so imagine the energy that the author will need to invest into his/her defenses. That is why we have intelligent mechanisms, that take care of maintaining the balance, without needlessly making havoc in people's lives because of "stealing books". Other than that, the main goal of various transpersonal forces (demonic, angelic, and all kinds of other spirits) is to find the channels for their manifestation in the world, so if you are a young (which usually means broke) magician full of potential, they don't care if you acquired information about them in an illegal way. They just want you, to work with them and invest your personal energy in fulfilling (preferably) mutual goals. They may or may not find a way to compensate the author if he deserves it. These forces are egregores same as money so they speak the same language which means there will be no misunderstandings.
In the last 10 years, I spent somewhere around seven thousand bucks on magick books. I gave many stellar reviews on Amazon which sold thousands of books. That may or may not give me the right to glance over the latest book of certain authors for free before I decide to purchase, and if there is a curse for that, I guess I will find a way to handle it or live with it. I just think that right now, in this historical moment, there are other, way more important things that burden our "personal accounts" for us to be worried about petty curses. But if you, a currently broke young magician have only 11 bucks in your pocket, and you decide to buy a book instead of spending it in MacDonalds on Coke and hamburger, that act will be seen as a serious sacrifice and it will echo through the eternity.