I still think it's a scam. Sorry.
But the real
scam is University bookstores. I refuse to buy from them. If I can not find a book cheaper online, but for the same price as the bookstore, I buy it online.
Uni bookstores overcharge by a lot and they know it. For a school that gets my 35k usd a year, they should be ashamed of the prices they charge for books.
And as far as authors getting royalties is concerned... I'm not. I am sure I'll get slammed for this, but the only bigger scam than the bookstore, is "So-and-so's 12th Edition Physics" or "9th edition thermodynamics."
Give me a break. The material is 300 years old... what's new? Oh you changed the order of the problems? You added some pretty new pics? Well, now that you put it that way, sure, I'll shell $200 for the newest genuine version