It may just be that particular shows from those names aren't selling and those shows in certain markets are on the list. Taylor Swift will never be on this list. I doubt Metallica is either. Granted I'm just a fan and don't know the insides of the business but if these Gn'R shows are selling as bad as people on here say why wouldn't you dump 1,000 tickets for $25 (this $25 promotion is almost always lawn /back of amphitheatre/upper deck seats with few exceptions) and get people in the building who will probably buy merch/beer?