If the advice in
that particular book is correct, then any entrepreneur who spends $100 on it will recoup the cost fairly soon.
If the buyer is a college student rather than an entrepreneur, well, the cover price is comparable to the price of other college textbooks. Textbook publishers can get away with charging a lot because students have to buy whatever the professor says to buy, and because once they’re borrowing tens of thousands of dollars for tuition and living expenses, students will not balk at a few more kilobucks for their books.