Vinita, It is strange that you yourself added this question and then first answer too is by yourself only!!
And your own answer to your own question clarifies the reality. NIRF data comparison for median salaries for IITs and IIIT Hyderabad is like comparing oranges with apples!
NIRF data is based on median salaries of all disciplines that are taught in an institute. IITs teach many disciplines (Including ECONOMICS and other humanities subjects too) while in case of IIIT Hyderabad it is just one discipline that is CSE. Now how can median salaries from IITs and IIT Hyderabad be compared?!
Bottom line is median salaries for BTech CSE from IITB is considerably higher than that of BTech CSE from IIIT Hyderabad.