Interesting, I am looking to get a z28 in Rally Yellow and did not know any of this. I also think charging extra for colors is nothing more than a cheap money-grab, since as evident from the Ultimate Factory show, the colors are not specific to any paint bay and can be changed at will. It doesn't cost them any more to paint black as it does yellow.
All they're doing is cashing in on demand. Which is weird, since Rally Yellow is one of the lowest-demanded colors.
But I agree, paint should NEVER peel or chip easily on a brand new car.