Even in a flat market, of course there is room for volume growth for the individual proprietor, in this case, the artist. But a flat market requires more competitive rules to avoid monopolistic tendencies. In the Swiss regime, the distribution of sales will smear out over more small artists and fewer giants. The long tail gets thicker. My brother is an artist. I'm totally fine with that scenario.

Even if the money spent is constant, the money is moving from the distribution cost (marketing, CDs, etc) to the artist (concerts) in the case I described above.

Concerts need to be marketed as well and it takes a lot of time to perform on stage (I used to help with that and have done some myself). So if you work out compensation per hour, I'm not sure if concerts are really a better deal for artists. My guess is that it is a better deal only for the long tail of less well known artists who make almost nothing from media distribution anyway.

I assume entertainment budgets are a constant percentage of total discretionary spending. So they go up as income increases with economic growth.

True, but real incomes have been stagnant in the US and many other developed countries for over a decade.