Out on Capitalmind, Deepak Shenoy has an excellent post on the penetration of banking services in India, where he points out that 30% of all bank deposits in India are in Mumbai and Delhi. I encourage you to read that post in full.
Having read that, I was interested to see the per capita figures and compare them across states. On a whim, I decided to compare that to per capita state GDP and this is what I got:
While the direction of causality cannot be clearly established, this clearly shows that banking penetration is highly correlated with economic activity.