Bundling of Mobile Handsets with Plans and in the way thus subsidizing the cost of hardware is something very common in the US & Europe. Aircel has introduced similar plan in India where in the cost of hardware will be just 50% if you lock-into a Post-Paid plan with Aircel.
The following chart shows the iPhone 4S Reduced Cost in India which will be 50% discount to suggested retail price in the Indian market.
With Mobile Number Portability, you can always keep your number and switch to Aircel from Airtel which is seeing lot of complaints these days.