Good article Rex, thanks for taking the time to gather the info.
I live in California, and can only really speak for this state. But you hit the nail on the head for our state, which is that the private ambulance costs and hospital bills are all you will be expected to pay, unless you were committing legal violations, which led to the rescue. CalEMA (now changed back to California OES) coordinates SAR for the state, but local Sheriff's Offices for the most part form the majority of SAR efforts, along with a few private organizations and federal agencies. I've been on SAR for 15 years, part of which was as a coordinator for our team and leader of our technical rescue team. We have never billed a SAR victim. Ambulances, on the other hand, are not cheap.
If an air ambulance is required, like you said in your article, it will be selected by the Ops Manager or IC, not the patient/ victim. But one thing to keep in mind is that CHP helos have a paramedic/officer on board, and are completely free. Coast Guard have an EMT-I, and are free, and CSAR helicopters (like the 129th out of Moffett Field), have a paramedic (pararescue jumpers), and are free. So there are a lot of free helicopters out there for rescue that do not cost the patient a penny. The downside is that availability/ protocols/ response times/ nature of injury will determine who responds, not free vs. costly.
A photo just for fun, of me and my K9 partner practicing "hot-loading" in a CHP A-Star helicopter at SAREX 2013. The only time I've been in a helicopter on an actual rescue is when I was hoisted up in a basket into a Coast Guard HH65, but that is a long story and involved a "recovery", not a rescue.