3) One theory that could explain a rise in ticket prices is this: since people AREN'T spending nearly as much money on CDs, they will have more to spend on tickets/merch than they would otherwise. This would represent a shift in consumer demand away from CD's and towards live shows (makes sense since CDs are no longer required to enjoy music). In other words, the price hikes are perfectly justified and reflect the demand of the fans. Why is this inherently bad or undesirable? People are voluntarily choosing to pay less for CDs and more for tickets, and hopefully the extra ticket revenues are going to the artist.
While this is a valid point to defend the rise in ticket prices, it really shouldn't cause them directly. Customers spending less on their at-home media doesn't necessarily mean we have more to spend ON LIVE SHOWS. That would assume our basket of goods (<==remember that phrase from econ?

) consists of: CDs, concert tickets, and....nothing else.
Really what's happening is a shift in the entire industry and the way it relates to consumers. To point a finger at any one facet is ridiculous. The customer's approach to music is much different today than it was 20, even 10 years ago. I have tons of music I would never have purchased on CD back in the 90s, because maybe its Banarama's "Cruel Summer" and I don't need anyone to know I have it, or maybe its because I like one song off the CD, but not enough to warrant the 15 dollar purchase. There's far more exposure now. But just because my iTunes library is bigger, more diverse, and more pirated--hah!--than my older brother's CD collection doesn't change that there are particular artists I prefer and will shell out the cash when they come to my city.
Plus, a big reason ticket prices go up when sales go down is because concerts aren't like other products that can be stored with no expiration date. They're a one time deal that comes with tons of guarantees for artists, vendors, etc. They have a small window to make back their investment so if sales are in the toilet for one show, the next one they'll be hedging their bets with small price bump.