I say that if the charge is high enough then folks will get the idea that SAR is serious stuff and not something to call for frivolous reasons.
Tricky - if you start charging for rescues it deters people calling for help until it's too late. Or worse people then trying to evade the rescuers to get back on their own.
Do you want people to call for help as soon as they are lost or wait until it's dark and they are cold, wet, hypothermic and even more lost.