And that's probably just modelling, you still have to have someone UV it, texture it, create the materials, animate it and get it working in game while being bug free. Adding wear and tear to cars is even more work, if you want to actually have the car take physical damage those are extra pieces you have to create and hook up. It's a long process, but the truth is a game like GT5 wouldn't sell well at all if the art wasn't at that standard.