The ticket was always underpriced
For forty years the gap between face value and what people would pay went to brokers. Dynamic pricing is an argument about who collects it.
Hold the anger about the price for one moment and ask where the money used to go. A sold-out show priced below what the room would bear does not stay cheap. It gets bought in bulk within seconds and sold on at the real price by somebody who will never attend a concert in their life.
That gap has existed for as long as ticketed music has, and for decades it was collected entirely by brokers. The face value was a polite fiction, and the fan who paid it was mostly the fan who got lucky, not the fan who cared most.
Dynamic pricing is the promoter declining to keep donating that difference. Whatever else is wrong with it, the money ends up with the people who built the show rather than with an intermediary who added a browser script. That is a better destination, and pretending otherwise requires nostalgia for a system that was quietly worse.
A cap does not remove the gap; it relocates it. Hold the price below clearing and the difference reappears on the resale market within the hour, which is precisely where it was before anyone objected to the practice. You cannot legislate away the fact that more people want the room than fit in it.
The real grievance is not the price but the surprise, and that is fixable without price control. Say the range in the announcement, show the all-in figure from the first click, and let people decide. Treat the audience as adults and most of the argument goes away.