This is a difficult question to answer. The pay rate depends on educational and real-life experience as well as the Behavior Analyst's ability to think on his/her feet and be effective with your child. I have worked with PhD's who didn't have a clue how to educate children with Autism or reduce their inappropriate behaviors because the graduates spent all their time reading books for school rather than working with kids. I have worked with people who had BA's in something completely unrelated to Autism and were great because they had great mentors and gained wonderful, hands-on, experience.
Today there is a Certification program for Behavior Analysis. The programs are typically costly and require a specific amount of experience, similar to the "practicum hours" of a psychologist, so you can count on rates similar to those of psychologists for those who are going through or have completed the BCBA/BCBA program.
A Behavior Analyst is typically not a tutor. If you hire a Behavior Analyst to work directly with your child, you can count on a hefty associated fee because the hourly is probably high. However, if you find someone you trust with your child and you can see progress in a reasonable amount of time, would you really sacrifice the teacher or program supervisor in order to save some money? Just as not all teachers are created equal, not all Behavior Analysts are created equal. Some people simply have the "it" factor that allows them to really connect with our kids.
When people are willing to pay hundreds of dollars for dog grooming and thousands of dollars on "snake oil" treatments to reduce wrinkles and cellulite, I would think investing in your child's education is pretty reasonable.
Temple Grandin once said that her success is in large part due to the great teachers she had when she was young and "a good teacher is worth her weight in gold."