The lack of knowledge about basic science is for me a major red alert when it comes from doctors or self-proclaimed 'health experts'. One of my favourites is when they talk about 'healing frequencies' and don't seem to understand that there has to be something changing state periodically, such as pressure, voltage, whatever. "I'd like a bottle of frequency please..." I encountered one naturopath who said that no one really understood electricity. If he managed to convince someone that electricity was mysterious, he'd be able to sell them whatever electrical tests or treatments he wanted to. He wanted $150 for what would actually be measuring skin resistance with a regular ohmmeter with a scale creatively remarked with various ailments. Squeeze the electrodes a bit more or less and you'll be diagnosed with foot fungus instead of brain cancer.
The creepiest alternative medicine encounter I had also involved electrical treatment. I walked into a health food store looking for a supplement. There was a bunch of people in the store sitting together in chairs, holding on to electrodes. One of them was telling the others "I can feel the cancer melting away!" I exited quickly, without buying what I'd come for. It was just too creepy. However, I'm pretty sure that some of those people came away convinced that some minor electrical pulses cured them of whatever they were sure they had.
As for the ones who spend the most being most likely to be 'helped', shelling out that cash generally means that they've already been convinced of whatever it is, and thus most likely to benefit from the placebo effect.