Where I live, it’s free for school children and people on welfare etc. For university students it’s 5€ a year, for adults it’s 10€.

So really not a lot, but you also get access to a lot of other online services for free (encyclopedia, streaming service for older and arthouse films, magazines etc.)

Late fees are just there to keep you from keeping a book or whatever for long periods of time, because then other wouldn’t be able to read them.