This spring, I had a conversation with a speech pathologist about my son and getting an articulation assessment for him. I think his rate was $90 / hour and said an assessment is usually about an hour, maybe more.
It took us a while to get scheduled (due to a lot of bad timing, including a death in the family) but between the initial conversation and actual appointment, my child had actually begun self correcting for the one area of concern. The day of the exam the pathologist interviewed me on my child's language development and history and also did a brief exam, in which my child got every sound correctly, including the problem sound.
The pathologist then told me that (a) my child was at the upper age range of saying that sound correctly and (b) that he WAS now saying it correctly, so he didn't think therapy was needed, but gentle reminders would work fine. (And, indeed, the reminders worked great. We don't even need them now.)
The time he took with the eval was so minimal he didn't feel it was appropriate to charge me.
This is all a very long winded response that "Yes, I think $120-$150 is probably the range for you." I wish I could remember better what was happening in the spring, but with everything going on, I'm happy to remember my own name.
The pathologist showed me a speech sound development chart, as each sound is clarified at different ages. It was helpful for me to see.
http://jwucommunicationasd.wikispaces.com/Wk1+sound+dev
http://www.talkingtails.net/SpeechSoundDevelopmentChart.php