What or which is the best IIT JEE Foundation for class 10? and what is the cost to study in an IIT?
It is always good to start with NCERT.
You should not start preparation for JEE aggressively from now.It is very important to have deep understanding and indepth knowledge of every subject and topic so better start with NCERT.
Also you have to do preparation for your class 10th which is equally important.
The fees in IITs is upto 1.20 lakhs per semester.
In total the fees in IIT is 12-14 lakhs for 4 years.
I hope this helps