> [...] not to pay for the actual cost of responding to a real call.

Not true for all places. There are places where the callee can be charged for the costs of a call and the owner of the building has to pay the firefighters (well, his mandatory government-issued insurance will pay). It's moving bills from one stack to another, but it's not free as in beer.

Depending on who is paying and how much, someone might light a small fire to avoid the fine.

I'd interpret the "minus first N per year" to mean that you get a few "free" fires per year - but after that your habits filling your closets with oily rags, overloading electrical extension cords, and smoking in bed will start to cost you.