While it's true that the prices are lower in the US, in this case you can chalk it up to the import duties and customs levied by our country.
There are a few disadvantages to buying the Sony PS3 from the US.
To start with is the most obvious: lack of warranty. If your system fails for any reason, Sony India will not be able to help. In fact, in many cases, Sony will just replace a faulty system rather than repair it-provided the system is under warranty.
Second: Input voltage
Unlike laptops and cellphones which now have universal power adapters, a Sony PS3 purchased from the US will likely have an input voltage of 110V (as opposed to 220V that is used in India).
To use such a system in India, you will need a 220V to 110V step-down transformer. While these are easily available, if someone accidentally plugs the system directly into a 220V outlet, the damage might be irreparable.
Third: Blu-Ray region locks
The Sony PS3 is a very capable Blu-Ray disc player, but Blu-Ray players are still region locked-meaning they will only play discs encoded with a specific region format.
There are three Blu-Ray regions; Region A for the Americas and certain parts of East and South-East Asia, Region B for Africa, Middle East and Europe and Region C for Central Asia, China and India.
If you buy a US-version PS3, it will only be able to play Blu-Ray discs in the Region A format.