By 'they' you mean Indian I guess. Four will be constructed by Mazgaon Dock Ltd in Mumbai and three by Garden Reach Shipbuilders & Engineers in Kolkata.
And you're spot on with the cost. But these are far more expensive than the Talwar Class frigs or even the Shivaliks because Lockheed Martin and Hyundai Heavy Industries have jointly responded to the Project 17A combat systems Request for Information (RFI) issued by Indian Navy. They have offered the Aegis Combat System to be included in its Project 17A frigate proposal.
Fair enough. But we don't exactly know the details of what goodies will be inside the follow on Talwar class. Who is to say that Russians haven't come up some AegisSki of their own.
Needless to say the $3 Billion figure is still speculative. It could be less, or the deal could include more than what meets the eyes.