that is complete bullshit. I have bought very good textbooks for a lot less when they don't come from one of the big publishers. The publishing companies rip us off by doing things like making a new edition with extremely minor changes, making people buy "codes" to access their homework, etc.
This book was written over 30 years ago by a guy who is no longer alive. It's on the ninth edition now. Most of the Math and Physics at the undergraduate level does not change much or at all in 30 years. There is absolutely no reason to by publishing a new edition of the book every 3-4 years.
The textbook for another class of mine was $35. If they can sell it for that cheap, then there is no reason that this one should be sold for $200 more. The publishers will sell the book for as high as the market can handle. If you go to india, the same book will sell for like $60. It has absolutely nothing to do with the "amount of work it took to write the book".
I just stole a physical copy of the book though. So I don't have to print this one anymore!