Daniel Gross has an interesting article in Slate on a long paper published by Princeton labour economist Alan Krueger.(Krueger's article is PDF and 86 pages.)
The nugget for me was the fact that the top acts make much more money from touring than selling records. How much more? It is difficult to get the numbers exactly right simply because artists may be touring to support a record that was released the year before; but 10x is not out of the question. In fact, for bands like the Rolling Stones, touring income is really the whole story.
Gross attributes this to downloading and, no doubt, that is part of the story; but the other part of the story is that the bands which are making their big dollars touring - for 2002 Paul McCartney, the Rolling Stones, Elton John - most are selling nostalgia to boomers. And those boomers have already got the boxed sets of the bands they like.
If you look at Eminem or Jay-Z the figures are very different with record sales exceeding touring. My bet is this is generational. The people who are actually making music rather than reselling music they wrote thirty years ago are actually selling records.
Krueger's paper covers a whole range of issues from CD sales to scalping and is a wonderful example of what real world based economic analysis can reveal.