STD calls are getting cheaper but it was never thought they would be as cheap as Vodafone are giving them. Vodafone which is India's second largest telecom operator are currently offering 50 paise per minute for STD, local and regional STD.
And example is that you live in North India and from there you purchase a bonus card (each state has its own price) and then call anywhere in North India for 50 paise per minute.
In Delhi a bonus card is Rs 74 with which you can make STD calls to Himachal Pradesh, J&K, UP, Rajesthan, Punjab and Haryana at 50paise per minute
But in Karnatka its different, and better as you can get a Rs75 recharge for 3 months of validity which gives a 50paise charge per minute on STD and local calls.