What's the difference between a fine and a fee?
In What Money Can't Buy: The Moral Limits of Markets, Michael Sandel argues:
Fines register moral disapproval, whereas fees are simply prices that imply no moral judgment. When we impose a fine for littering, we're saying that littering is wrong. Tossing a beer can into the Grand Canyon not only imposes cleanup costs. It reflects a bad attitude that we as a society want to discourage. Suppose the fine is $100, and a wealthy hiker decides it's worth the convenience of not having to carry his empties out of the park. He treats the fine as a fee and tosses his beer cans into the Grand Canyon. Even though he pays up, we consider that he's done something wrong. By treating the Grand Canyon as an expensive Dumpster, he has failed to appreciate it in an appropriate way.
Or consider parking spaces reserved for use by the physically disabled. Suppose a busy able-bodied contractor wants to park near his building site. For the convenience of parking his car in a place reserved for the disabled, he is willing to pay the rather large fine; he considers it a cost of doing business. Although he pays the fine, don't we consider that he's doing something wrong? He treats the fine as if it were simply an expensive parking lot fee. But this misses its moral significance. In treating the fine as a fee, he fails to respect the needs of the physically disabled and the desire of the community to accomodate them by setting aside certain parking spaces.