We ran the gamut with voice teachers. The first one, back when dd was about 12 (and she only took her that young because she knew her from school) and she was about $20 for 45 mins. She didn't really teach dd much other than proper posture and breathing. Otherwise, dd could have damaged her vocal chords.
Then, once she got 8th grade, she moved to real voice lessons. Those were more like $35 for 45 mins. But the lesson routinely ran longer.
Dd then felt she had been taught all she was going to be taught there (although she loved this woman to death!!) and she moved on to a 'professional'...and man, that woman never let you forget it. She had sung in operas in NYC. Okay....that's nice. She charged $55 an hour for the first year, then her dh became unemployed and her rates went up to $60 an hour!! Now, this woman was about 25 mins away, and the gas was not cheap. And, dd didn't feel that she was getting much out of it.
So, she moved to a new person here in town, that charged about $40 an hour...and worked with dd when she needed something special for school or an audition. She worked with her when it came to auditioning for colleges. The previous coach couldn't have cared less. Dd still tries to get a lesson in when she comes home for long periods now.
I'm sure it's regional, and that here in NE it's probably more expensive than in the mid-west....simply due to the snobbiness that seems to abound here. I would try to find what coaches are charging in your area...go from there.