Your point about religions taking from each other is true, except that Hubbard pretty much, from some reading I've done since this started (which reinforced inklings I'd already had) seems to have worked up scientologies entire spiritual teachings from Ordo Templis Orientis documents stolen from Jack Parsons. Which, basically, means Scientology is Thelemism, but written up by a bad sci-fi writer with a huge desire for cash rather than a drug crazed bisexual poet with a huge desire for fame, which makes some sort of sense.
As for the second part, of course you don't need expensive herbs or auditing or anything. How are you supposed to understand how a magickal system works if you don't do it yourself? To rely on others to provide your spiritual guidance and self-improvement leads to charlatanism and the accumulation of political power by religions. Which are bad things. Whilst I accept your criticisms of the placebo effect or feel good factor, I think you're overlooking its flipside, which is the numerous reports and studies showing that people suffering from depression or anxiety are much more likely to contract diseases or develop other health problems, not to mention drink, smoke, take drugs, eat fatty foods etc. more. Keeping a positive spiritual equilibrium has definite real world health benefits, and the method you use to achieve it is entirely personal to you. That's why religions subjective. I don't like Scientology precisely because you don't need expensive auditing and courses. Just take up Satanism or something, its much cheaper, and there's almost certainly going to be more sex involved.