Taxes/fees/charges for an I class fare should normally be the same as for J class.

Now perhaps what is happening here is related to GST and what fare this is calculated against?

https://www.flyertalk.com/forum/brit...tax-india.html

I did some dummy bookings for BOM-YYZ rtn and:

BOM-LHR-YYZ all I class:
Goods And Service Tax - India 22,691 INR
Development Fee - India 850 INR
User Development Fee - India 329 INR
Passenger Service Fee - India 409 INR
Passenger Service Charge - United Kingdom 5,688 INR
Air Travellers Security Charge - Canada 1,399 INR
Harmonised Sales Tax - Canada 176 INR
Airport Improvement Fee - Canada 1,349 INR
Carrier imposed charge 26,692 INR
------------------------------------------
Total charges 59,583 INR


BOM-LHR-YYZ all J class:
Goods And Service Tax - India 56,420 INR
Development Fee - India 850 INR
User Development Fee - India 329 INR
Passenger Service Fee - India 409 INR
Passenger Service Charge - United Kingdom 5,688 INR
Air Travellers Security Charge - Canada 1,399 INR
Harmonised Sales Tax - Canada 176 INR
Airport Improvement Fee - Canada 1,349 INR
Carrier imposed charge 26,692 INR
------------------------------------------
Total charges 93,312 INR

So it seems the difference is the GST which is 33729 INR higher as it is calculated as a percentage of the fare.