I guess I make a distinction between what I would call "traditional" (for lack of a better word) homicidal violence---gang murders, drug murders, you-dissed-me rage murders, etc.---and people, especially, kids killing because, e.g., their parents impose a curfew.
People may not consciously think life is cheap, but I believe growing up in a culture infused with the idea that if someone, even someone YOU had a part in creating, is inconvenient for you, it's okay to kill that person and throw him in the trash, has consequences. For everyone.