Re: Why is it
15 bucks is not bad for a set of rings....
I'm sure you could find aftermarket rings and pistons through Wiseco, they make rings and pistons for virtually anything. I guarantee they'll be more than 15 bucks.
As for the other stuff- I think you could find a tensioner for around the same as dax, but maybe better built.
You won't find a mag replacement or CDI for less than 50 as far as I know....most CDI's (there are basicly two kinds- two wire and three wire) go for around 50-100 dollars.