Part of it is fate and just random, but it's also fueled by the fact that last year was such a bad year for the industry. This year, a lot of acts were reluctant to go out right away,
You don't normally see three huge acts like that out touring in the same year. McCartney and The Stones alone really helped drive up ticket prices.
Ten or 20 years ago, the acts that sold a lot of records were also the big concert ticket sellers. You don't see that correlation today.
These older acts are the gravy train, but someday that train is not going to run anymore, and no one really knows what to do when they're gone. Of the young acts, you have someone like Coldplay who does quite well, but where will it be in 10 years? That's hard to say.