I was actually admitted to SSI. When the time came around for classes, I soon realized that the whole program was just a programming course taught by a Harvard student and at 10x the pace of a typical programming course. It got way too fast for me to keep up and I ended up dropping out. SSI is the type of program you attend if you couldn’t get into any better summer programs. Didn’t find anything valuable about this program and I strongly do not recommend it. It’s run entirely by college students, and I think there were a couple posts last year about how it was not worth the money. 
This thread is def coordinated by the founders given that they posted the exact same thing in another thread asking the same question. There are many other more established and legitimate programs for half of the cost. Even if it is as amazing as you claim it is, there is no way it’s worth that 6.5k price tag. There’s a similar program by Dr. Serena McCalla called the iResearch Institute and many of her students have won awards at top competitions like ISEF. I hear they’re more generous with their financial aid than SSI.
Also thought I’d drop some resources I used to learn more about research and opportunities instead of this camp:
- A free, school club based program (about research, publication and science fairs) https://restem.ysjournal.com/
- A directory of basic info about the process: Advanced Project Guide
- A list of legit, competitive camps: Summer programs | MIT Admissions