This guy retired on $800k raising a family of 3 with $25k/year of passive income: http://www.mrmoneymustache.com/2012/01/13/the-shockingly-sim...
Specifically, it is generally assumed that a diversified investment portfolio will earn ~4% after inflation on average, and by spending 4% of your portfolio balance at any time you are reasonably safe in the assumption that your money will not run out. At 3% it's all but assured that your money will not run out. These are conservative assumptions and take into account the fact that in any given year your investment performance could be significantly less than 4%
Turned out those savers were the suckers needed by those banks, in an attempt to remain solvent.
If I'd opened a bank account last time I visited India, converted sterling to rupees, to saved in an Indian bank account at 12%, I'd end up less pounds than I started with.
Putting money in consumer banks in India really only makes sense if you live there.