There’s a market price for everything, including NFL game tickets and concerts by pop stars.
If she can’t sell out, based on supply and demand, the price of tickets is too high.
She would have sold out all shows if the tickets were $10. I don’t know how prices are arrived at for concerts by pop stars, but, clearly they misjudged in pricing for her, assuming the goal was to have sold out shows.
Selling out the venues is not the measure of correct pricing. Technically you could sell tickets at fixed prices until the end, and then auction off the remaining tickets, and therefore make a bit more money.
But if the fans know there’s going to be cheaper seats later, they might not pay for the expensive seats.
There may not be a price point lower than $500 that makes more money for them, even selling more tickets.
If you can sell 8000 tickets to a 10,000-seat for $500 (4 million dollars), you made more than if you sold 9000 tickets for $400 each, or sold out at $350 each.
You might do variable pricing, but once you offer lower-priced tickets, it can be harder to get anybody to pay for the higher-priced tickets.
The other consideration is whether you want stories like this one, because music is in large part a matter of good publicity.