I've always felt that if I'm going to carry a gun, I need to be prepared to protect myself and those around me if I feel there's a real risk and that I can take action without making things worse.
If the person seems really interested in just robbing the place, I'd probably not take action. As others have stated, $200 of insured money is not worth taking anyone's life over.
If he's actively waving the gun around and making threats to everyone in sight, then I'd be more likely to get involved.
If there are multiple people between me and the BG, I need to be able to move into a position where I can make a safer shot. That may not be possible.
An idiot with a gun robbing the place, to me, is not an automatic "draw your gun and get involved" situation. There are a lot more variables than that.
There's a fine line between defending against a legitimate threat and trying to be an action hero.