No, It's not "Free"

Why is it that you can buy diet soda, that is sugar free, caffine free, sodium free, but it still costs the same as the regular kind?

It seems like we should get some kind of discount for the stuff they took out, like when you buy a car without a sunroof, a/c, CD player, etc.

If it were free shouldn't it look like this?


Also, when I get one of those (no, it doesn't happen very often) it still cost the same as a Pepsi the same size. There has to be a lot less cost going into "making" water than making Pepsi. I'm confused....