Hi, our private SALT was about £45 per hour, but that was about 6 years ago in Greater London.
DS was observed in nursery. By local NHS team. I felt they were too wishy washy about it all, and I needed something done pronto.
DS also has mild epilepsy and was seizing at the time and any language he had (not much) seemed to regress after every seizure cluster.
So we went to private for an observation and just stuck with it. It was one of my finer parenting moments! I am not an SALT but I knew my son and I could see something wasn't right and that the NHS was being too slow in my mind.
IME if speech is not coming along as per the norm, the chances are that comprehension, listening and other social skills with be behind too.
DS also had group SALT in school until the end of yr 4. I also put him into Kiddie Drama classes. Which he loved. I was encouraged to get him involved in as many activities as possible. To encourage him to communicate, listen, take instructions, make friends and improve all his soft skills.
He could still do with some SALT age 9 now, but I have just signed him up for some more drama lessons. He speaks fluently, but struggles a bit with literacy comprehension and does not like reading. Despite being able to read beautifully, his tone is great, but he finds it difficult to read "between the lines". So there is still work to be done.
The work that a good SALT can do is amazing and I still marvel at what they can do. Do remember, that your child will grow and develop too so they will bring themselves along. Our SALT managed to open the doors that let our DS learn to communicate.
HTH. xx