@ how much to charge, screw it, charge above the rest. If people don't want quality, fuck 'em, let them spend twice the price by buying rubbish articles. People do realise that it's a false economy buying cheap articles, but unfortunately not everyone. However, I get enough requests as an article writer to choose my price, as long as it's not too much over the average here. I generally charge about $8 per 500 words, although even that isn't brilliant.Usually I can get through generic articles with a couple of rewrites within half an hour but I've been in that same situation writing on things I don't know about and its taken hours to get decent content together. Its even more frustrating when you're working for a pitiful income but honestly even writing for content mills is a step up from my last job. I don't even know what to charge, everyone seems to be able to do more than me for a fraction of the cost.
As for why, I do get more satisfaction in writing than I would working a job outside and it wouldn't be nearly as flexible. I wish I could find some room to progress at the moment though. Even with writing articles I think I'd be happier writing for someone with quality control who had no qualms telling me when I fuck up. At least it gives me room to improve.
P.S. I don't know how far into your writing sales you are, but one thing I thought of today that might be good, is to instead of offering review copies to the millions of serial reviewers, as a perk of the job, you can simply publish a review copy for all to see, and let people make their decision on that. Simple idea, I know, but I don't see anyone doing it, really.
Joe