Personally I've never left an event earlier, whether it's a concert, football match, etc.
I think of it as a mix between having a good time and respect for those you are watching (god knows how hard that is in football sometimes). However, who am I to tell someone else that 150$ is an expensive price to see one or two songs live? It's all about the personal experience and how much you're willing to pay for it. For most of us the experience ends at Paradise City, for others after SCOM.
It's all good - we're happy, they're happy and the legacy of GN'R lives on.