Chris142,
This is my theory:
People in general equate a low price with low quality. So then the marketing folks will raise the price up to meet their competitor's price in hopes of more sales. Guess what? IT WORKS! The guy that walks into the auto parts store, sees that CS is almost the price of GTX, and thinks to himself: "hmmm, this CS must be pretty good if it's priced the same as GTX." So then he walks out the door with a case of CS.
Then you have the very clever marketing executives that assign a high price to an oil, then offer it at a discounted price or rebate, when essentially the oil is only worth the discounted price to begin with.