Age of Low Cost Mobile Connectivity ??

I have been noticing a steady pattern off late (atleast in TN where i live). Starting with Tata Docomo entering the market a few months ago, the telecom industry has is slowly seeing categorization. And surprisingly it is much similar to how Air Deccan came into mainstream with its concept of a Low Cost -No Frills services. First there is the big 4, Vodafone, Airtel Aircel and BSNL forming what could be analogous to the premium service providers like Jet, and AI(if you call it premium that is). They come with good connectivity and a bundle of VAS that most technology addicts like me have become completely dependent to. And then there is Idea, Docomo, MTS and the new kid in the block Uninor. surprising how on an average a local call cost offered by this group of service providers is somewhere near the 40 paisa mark and STDs in the 80 paisa mark. Compare this to the Vodafones and Airtels which usually will cost you between INR 1 and 1.50 a minute. Some people may argue about rate cutters, bonus recharges etc, but the point is, in its most element form, Uninor's Full tariff is lesser than a rate cut vodafone. No surprise thus, that uninor does not have any special perks, no frills, no VAS. it does not even offer GPRS. but who cares, if you want a phone to talk, and you usually talk a lot then this might just be the thing for you. If you however want something more than just a key and call phone, in other words if you want mobile internet, then you will have to stick with the biggies. What however completely confuses me is, why is it that airtel and vodafone are jumping into the bill per second mode. Are they feeling threatened by the DoCoMos ?? if so why? arent their target group completely exculsive of the target group that the DoCoMos and Uninors look at? If they are only worried about the new ones eating into their market share, shouldnt they be doing something in the VAS segment to hold on to their customers rather than joining the party and changing their billing scheme?? weird.