What can I expect to pay for massage therapy?

What can I expect to pay for massage therapy?

I have ongoing back pain, which is probably due to a combination of stress and bad posture. My friend sees a massage therapist once a month and I'm beginning to consider doing the same. I know what she pays, and it seems expensive. I'm curious, is there an average? What's a fair price to pay for a 60- or 90-minute session?