This is going to sound horrible,

...In my case (most of the time),It's been someone has backed out,someone won tickets,we knew someone that was working the concert,the tickets were usually given to me, or someone else paid for them. At times I've offerd to pay for the tickets,but ended up paying for the ride to get there,gas,etc,etc...
Part of the problem is I don't live in a big city,and most acts tend to go to Tulsa,Little Rock,Columbia,St. Louis,Kansas city. So $50 a ticket (low end),$50- $100 to drive to go see them,Typically a hotel,or motel to crash at..I've REALLY got to want to see that person...
There are few concerts I'd love to see...Kenny Chesney,Garth Brooks,Paul McCartney,U2,Sammy Kershaw,Toby Keith,the Who,Def Leppard,Bon Jovi,Heart....
Then there is that list,that maybe 10 years ago I'd loved to see,but now that I'm older (and they're up there TOO)I'd probably pass on now... Kiss, the Orginal Black Sabbath line up,Ozzy by himself.
I'm too much of a pussy as I've gotten older to put up with the people at the concert,and don't think the show would be that great to put up with the idiots...