I have to add two caveats to my opinion...I do volunteer SAR in a non-mountainous area, which subtracts the cost of a lot of personal gear, and I also "work" primarily in areas with a dense canopy, which negates the use of air resources. I can certainly understand how both factors can add a lot of cost to a rescue mission.

That being said, I shy away from the prospect of SAR agencies charging for their services, even if only to offset the cost of team gear and medical supplies. My professional life is spent as a paramedic and EMS educator, and every shift seems to abound with patients who are reluctant to seek medical care (in some cases, much-needed) because of the cost it will incur. I have unfortunately seen people die or have otherwise severe problems because of not "catching the early show" and getting the problem fixed before it becomes a life-threatening one. My fear with charging for SAR ops would b similar; people who need help would wait until it's too late to call for it out of fear for financial ruin. I think it's important to remember that backcountry travelers are in a distinct minority in the US (so I gather, have no stats to back it up), and charging a small group of "customers" for the costs of training and maintaining a state of readiness would soon approach astronomical for the average person.