That kind of model is unfortunately common for university courses. I had it for my language courses, and a couple of the core maths courses.
The online platform justifies a subscription by providing additional resources, homework grading, etc. Fair enough, honestly, if they want to charge you $15 or something reasonable. But when textbook access gets rolled into the bundle, it tends to inflate the subscription cost and also have the convenient-for-the-publisher side effect of temporary access to the text. Lose-lose, from a student perspective.
I had a course that required we buy a license to Pearson’s service in order to submit homework. $100+ to view a pdf for a semester and submit homework through a buggy form interface. I still hold a grudge against everyone in the department for that decision.
It's just a coffee (startrek.website)