I went through the spreadsheet as well that you have mentioned.
I didn't understand it completely. You have mentioned two cases:
One is buying house of 1.5CR and the second one is paying 60K/M as rent and invest the difference amount.
1. You will end up with just a house(Now the future value of that house is debatable but I think in 15 year 1.5CR house will definately cross 3CR).
2. You will be paying rent for the 15 years as well as putting the difference amount in some investment.
There we are ending up with 3CR (Investment returns)
How does it indicate to go for the second option?