It's as fair that you can refuse to pay $60 as it is for the author to ask for it. It strikes me that most people who would pay $30 would also be willing pay $

It's as fair that you can refuse to pay $60 as it is for the author to ask for it. It strikes me that most people who would pay $30 would also be willing pay $60 in this instance, as it's not as if many new C books are coming out nowadays. So I'm guessing that the author will do better at $60. Medieval notions of profit and the physical costs are mostly irrelevant, but the effort and expertise of the author are not.