The note seems so, I'm not finding the right word, but like playing games. Will he even know what you are talking about?
If you want to continue with this counselor how about going to the next session and simply state "I felt very invalidated when you addressed payment matters at the end of my appt. after I shared xyz. In the future, please address these matters at the beginning of my appt." See what he says.
If you don't want to continue with him as a therapist and you have a grievance write a grievance letter. Simple and to the point. "I do not think addressing payment issues at the end of an appt. is appropriate or professional. I felt invalidated. I will be looking for services elsewhere." If he is part of a network/office then they probably have a written policy on grievance procedures they'll show you if you ask. If he is in private practice - maybe not.
I think it was very bad timing too btw. I would have felt invalidated too. If this is his only 'mistake' and you like him in general maybe he just had a very bad day. If there are other things it is OK to look for a better match in therapists. Just because you've known him for so long doesn't mean he is the counselor for you. I've only seen two counselors in my life so I'm not expert but they both said that if I felt it wasn't working or wasn't a good match to speak up and they'd refer me to someone else. It happens. It is expected. There are a lot of different styles of counselors out there - lots of different people. The person before you may have had a grievance for mentioning payment issues at the beginning of the appt. instead of the end - She might feel like it was starting the appt. off on the wrong foot and how can she bear her soul to someone that is worried about his payment!!
Who knows but I just think you'll have a better chance at feeling like there was some resolution if you are more upfront.