A recent post of mine explored the market for restaurant table reservations. Restaurants in high demand with long waitlists for tables could increase prices so that the market more easily clears. For potential reasons discussed in the article, they do not do this, which leaves the door open to third parties to buy and sell reservations for a profit.
The same economics applies to third-party concert ticket sales containing add-on fees. With popular unrest about the prices of event tickets with added fees...