My take as a former professional classical musician is to say that your idea of PR boosting ticket sales is not valid for (at least most) classical music. That's not to say you're incorrect, just to add a different (hopefully slightly interesting) perspective from another genre with a very different audience.

One reason for this is that classical music is focussed much more on the music than the musician, when compared to "popular music" (what's the best term for non-classical music that doesn't sound patronising?). Sure, Yo-Yo Ma or the London Philharmonic can attract people based on who they are, but even then a lot of decisions to see them or buy their recordings will be based on what they are playing. If you're a Katy Perry fan, chances are slim that you really want to see her live, look up a concert, then say "ah, but I'm not a fan of those songs, I'll give it a miss".

Another reason is probably range of repertoire - again this comes down to caring more about the music, not having the piece tied directly to the person/group who always performs it. If you love Francois Couperin's music, you're going to find it a lot easier to buy recordings than find performances. I suppose the same is true for indie performers, but I think a classical listener is more likely to find a wider range of classical music that's hard to see live than the equivilent situation for indie music.

Probably plenty more reasons too, but not too much off the top of my head. Oh, and demand I guess. A classical music concert will typically either perform once, or perform a short run, or perform a few times in different cities (or countries). That's the case even for the very biggest performers. A big pop performer, on the other hand, can do a much longer tour, and can sell far more tickets for each.

As to recordings, I think classical recordings have a longer shelf life - sure, some people still buy music from the 80s, or whenever, but much less than around when it was released. Whereas classical music, all the music is so dated (not in a negative way, just literally) that who cares if it was recorded a month ago or thirty years ago, if it was originally written centuries ago. On top of that, I suspect classical music listeners are less likely to pirate music. Possibly that's a generic snobbish view, but I think it's accurate.

When people talk about artists compensating fewer sales with more concert revenues, they always forget that not every artist is an indie rock band - there are genres that are less likely to be enjoyed live.

For instance think about that ambient, downtempo artist whose music is primarily meant for quiet listening sessions at home. Furthermore I could very well imagine that this kind of music and probably a lot of other niche stuff won't make their listeners buy fan shirts - there are genres that are less suited for live gigs and whose audience won't be attracted to merchandising.

To cut it short - what may work for a majority of artists isn't necessarily the solution for everyone and shouldn't be considered as a general fact that compensates for lower sales revenue or even justifies it.

The group (user) consensus on music seems to be that it should be, for the most part, accessible for free, and that live shows are how music is expected to be monetized. That seems like pretty ridiculous and greedy reasoning on the behalf of consumers. You're essentially eliminating one large revenue stream, in hopes that it generates new business in another revenue stream. While labels certainly rake plenty of revenue away from the artists, I think people largely underestimate the amount of money recorded music brings in to musicians, producers, songwriters, etc. Many people who are either not part of the tour, or who cannot tour, are going to be adversely affected by the incorrect idea that the music industry is zero-sum and revenues will just shift accordingly for all. If that were the case, the labels would have been on board a long time ago and 360 deals would be significantly more prevalent than they are.

There are lots of revenues to be lost by reducing, or making free, the cost of recorded music. How much is the Beatles catalog worth (in terms of albums sales, not licensing) and what is the lifetime value of their album sales vs. their touring receipts?