Are Airtel’s 4G rates cheaper than 3G rates? Why?

Bharati Airtel has been the leading Indian telecom service provider in India. But now it is said the high consumption users can enjoy the cheap rates for 4G services which is lower than the 3G services of the other competitors. But I wonder why are these rates suddenly cut down? Are Airtel’s 4G rates cheaper than 3G rates? Why?
