My calculation is fairly simplistic
break-even: where (money earned since MBA - cost of MBA) = (money earned if I did not do MBA)
1. I know how much I made post MBA, since Aug 2008.
2. I worked out a value of how much I would have made if I did not go to MBA.
3. Break-even is where 1 = 2
Also keep in mind I was earning in US $ before I started my MBA, so this isn't a case of foreign exchange trumping Pre-MBA Indian earnings.