Hello aspirant,

As you’ve not exactly mentioned which Specific IIT fee structures you are talking about and what details you‘ve read. So hereby I’m attaching a link of all the IITs and their fee structure according to their academic duration and the various departments concerned.

https://www.google.co.in/amp/s/engineering.careers360.com/articles/iit-fee-structure/amp

This will give you an insight as well as help you to compare according to your interests.

Hope you find this useful.