my 2017 son did the NTIS in his 15u year. USA baseball uses different dates so he was considered a 16u for them. he went through 2 rounds of tryouts and was selected to go to Cary, we went down there and had a great time. Very good competition, lots of schools there in attendance don't have any real regrets as it was a good experience.
I don't recall the exact cost structure but we enjoyed the experience and would have considered it again last year but had a conflict with the date. I certainly wouldn't consider it a mandatory stop, you are not going to make the National team...it is glorified fundraiser but it can have it perks as well.
At the end of it this whole baseball ride - IMO it is just part of a life journey for your son and family. If you can afford it, your son has some ability I found it to be nice couple of days. USA baseball, PG, PBR and all the others are just tools to be used, the cost is relative to what you want to accomplish and what you have to spend.