Cost is not just in terms of equipment.
Talking strictly financially and ignoring the human aspect:
We will lose soldiers. Kargil casualty was around 2000 (?) , I don't know what this war will do but whatever it is - The reparation to their widows, lifelong pension , other benefits, etc will be a hefty chunk.
In a full scale war - We will get hit. It is inevitable. We may lose a refinery, a port, maybe satellites if chinks get involved, I don't know what. But there will be damage for sure.
Some investors will run away. Impossible to model loss in any meaningful way. Investments have a multiplier effect. 10-100x depending on what study you refer to. We will lose some.
Markets will tank. Many people will be financially troubled as a direct effect.
I am not undermining India or Indian defences in this post. All I am being is a realist and trying to say war is costly. But cost should not be a factor when it is a question of survival. I have been the Pahalgam, my parents have been there, my wife has been there and one day my children will go there as well.
Those 25 were on the wrong place at the wrong time and I don't want my family or me to be at the wrong place at the wrong time within our country.
Civilisation began as people herded together for safety. The strongest was chosen to lead and protect, that slowly evolved into the strong being Kings and now Head of states - (then physically strong and now politically). Safety & security is the #1 duty of any state and the state must deliver - at all costs.