Just because there are greater "evils" out there doesn't excuse lesser ones.
It's calculus, which, as invariably gets pointed out in discussions about overpriced textbooks, hasn't changed much in the last century. How much value does that textbook actually bring over other calculus textbooks? Enough to justify a $20 million house? Does it present new and exciting ways to look at calculus? Does it make it that much easier for students to absorb and understand the material? Or is it successful mainly because of political skill inside a cartel-like industry?
Lot's of shitty books of all kinds sell because of good marketing. It wouldn't be a phenomenon exclusive to textbooks.
That said, there are huge differences among calculus textbooks. I don't know the one mentioned here, but when I studied, there was a choice between a very concise and condensed one, and a very drawn out and long one. The latter would have bored me to death. It is not easy to present maths in a short and concise way.
It's calculus, which, as invariably gets pointed out in discussions about overpriced textbooks, hasn't changed much in the last century. How much value does that textbook actually bring over other calculus textbooks? Enough to justify a $20 million house? Does it present new and exciting ways to look at calculus? Does it make it that much easier for students to absorb and understand the material? Or is it successful mainly because of political skill inside a cartel-like industry?