Taylor Swift can’t realistically play more shows than she did during the Eras Tour, and it’s unlikely that she’d have sold a million seats in London if she were charging much more than she did.
That's only if the event sells out. The ticket should have sold for a higher price such that the demand was exactly the number of seats available.
They ended up being acquired by a company that was much more into charging top dollar to big-spenders (which was ultimately acquired by Live Nation), and that whole category of festivals is now largely dead in Australia.
It's no good optimizing for simple supply and demand in one year if it destroys the product and therefore demand in subsequent years, which is what we're seeing the market. I'm familiar with libertarian principles, but every libertarian economist I've paid attention to has emphasized the importance of second-order effects.
Taylor Swift can probably still sell out if she raises the price ten fold, but what kind message does this send to her average listeners? What does it mean if the most popular popular musician of our times prices the populace out? You can of course dismiss the likely negative responses as emotional and irrational, but that's the whole deal with art and culture. You can't build a fan base without catering to their emotions.
And then on the other extreme of music you have people like Fugazi, whose low ticket pricing is very obviously a part of the band's entire artistic and ideological project.
If you want to see what happens when you apply supply and demand to ticket pricing, you can just look at your nearest big league sports team. The recent trend seems to be jacking up the prices as much as they can get away with and catering more and more to VIP guests who spend a fortune in one of those "hospitality" suites. Perhaps not a coincidence that less and less people, especially younger people, around me are casually into sports these days. They got told that they are not welcome in the corporate owned sports venue and they take their attention elsewhere, and all it's left are a dwindling set of diehard fans and C-suite people who are there not for sports but for overpriced steak dinners and are too nicely dressed to cheer for their home team.