Broken, I see Parody is like a genre. You are saying that parodies should not exist. Its the same as saying that Fantasy books should not exist.
People want to read parodys - thus they buy them.
Parody is when you make fun of smth that people know - and HP just happen to be smth that many people are aware off. THey buy books cause they want to read them - noone is making them.
Is it just for the money?
Do you think JKR wrote Harry Potter just cause she wated people to hear about this wonderful idea that she had?
And you can see that this doesn't bother her.
Hmmm....if its so easy to write a parody, why isn't everyone doing it? 8)