As always with this kind of question, it depends...
FWIW, I'm paying £35 an hour, which I consider very reasonable. But my teacher (
http://www.mikehall.co.uk/index.html) is head of jazz studies at RNCM with a huge amount of both teaching and playing experience and that kind of expertise doesn't come cheap. I only go 4 or 5 times a year and always come away with plenty to work on over the next few months. If you haven't done that much music before you might want more frequent lessons and then cost would be a more significant issue.