Ding ding ding! We have a winner. BTW, isn't it great how the professors write their own $125 texbooks in which they regularly make superficial changes to thwart the used texbook market?
I have seen them switch the order of chapters and nothing else! Though it's very much the publisher and retailer who gouge students the worst, then blame each other.
The better professors have moved away from texts and simply hand out lecture notes, or post them online. Moreso in graduate courses, however; undergrads pay greatly for those mammoth "intro" books.