Nikhil, valid point wrt to investment. However investing in "upgrading" fighters is not the same as inducting a whole new type. There is investment in infrastructure to support the new type, investment in a new set of weapons to support the new type, investment in pilot and airmen training on the new type, etc. Infrastructure takes the big chunk of the investment cost here, which upgraded MiG-29s and Mirage 2000s do not have to do. They slot right back into the airbase which has all the infrastructure set up. Also for crew trained on the legacy MiG-29 and Mirage 2000...again the investment is minimal when operating the upgraded type.
With the Rafale induction, the whole set of investment has to be repeated - base infrastructure (special shelters are being built to house two squadrons worth at each air base - Ambala and Hasimara), new weapons (Meteor, SCALP, etc) and training of crew - pilots and airmen. One can see the progress of the construction on Google Maps at both airbases.
The last new type that was inducted was the Tejas Mk1 when No 45 Flying Daggers
Squadron was raised on 01 July 2016. Prior to this induction, was the Su-30MKI when No 20 Lightnings
Squadron was raised on 27 September 2002. That is almost two decades back. So Karthik S is right ---> there has not been any addition to the *FIGHTER* fleet since the Su-30MKI. Today, the IAF has just one squadron of the Tejas Mk1 and has more than 12+ squadrons of the Su-30MKI.
There needs to be more inductions of Netra AEW&C aircraft (one is pathetic), more refuellers, complete MAFI (Modernization of Airfield Infrastructure) programs at all airbases, increase orders of Astra Mk1s, increase the number Tejas Mk1As (83 is too little)....the list goes on. The most important cost (and often overlooked on BRF) is human resources. There needs to be a greater intake of pilots into the air force. No point in inducting any of the above, if your pilot shortage is acute.
To quote Saab's marketing line ---> a fighter is only effective when she in air. So 114 Rafales or 114 Tejas Mk1As is pointless, if you do not have pilots to fly them. And the IAF suffers from a severe pilot shortage. Statistically, if memory serves me correct, there is less than one pilot to every plane. The PAF has the opposite - they have more than 2 pilots on average to a combat plane. I do not know about the PLAAF, but if you ask them...they will tell you it is fabulous!
The situation in the IAF is acute because of the lucrative growth of the civil aviation market. Challenging to match the pay and the perks that the civil aviation industry offers.
So while one can argue on the merits (or disadvantages) of inducting 114 phoren fighters, however the above issues are equally important and also need to be addressed. A fighter aircraft - phoren or desi - is only good as the support platforms that assist it. So trained pilots, trained ground personnel, increasing serviceability of present types (across the board, a 75% serviceability must be the goal), weapons stocks for a minimum of 10 days of intense air combat, AEW&C aircraft, refullers, modern airbases with hardened shelters and SAMs, etc are all important for an effective air campaign.