My friend the thing is generally known as "Gaadri". It is one of the most important things in your car. You can say that the engine rests on it and it should be expensive as well. Around a year back, one for Honda Civic 2005 was for 40,000 from the dealership and around 20,000 for Kaabli.
But, I think it should not be changed just because of rust. It is made up of some solid steel and is obviously exposed to water and moisture.
