If you want to get ideas for your area, just ask around. If there aren’t other harpists ask guitarists and pianists. You should get at least as much as they do.
If you want to pay bills, you have to charge enough to live. Since we can’t gig 40 hours a week, that means the hourly rate is usually quite a lot higher than someone who has full time work with benefits will get.
I live in what is currently the third most economically depressed area in the US, incidentally. Flint Michigan is doing better.
I wouldn’t put a lot of faith in those articles, incidentally. Most working harpists think those surveys are nobody’s business and either don’t answer or give quasi-bogus answers.
Incidentally, I didn’t mean of course the doctor didn’t object because he was getting a bargain. I just meant of course he didn’t object. He hired a professional service and there was a charge for it. Doctors can understand that. 🙂