So, a little context as to how the live events industry works, because it is not how most would assume.
First, you have the venue. The venue has an owner. This may be the owner of the sports team who plays there, a company that's entirely unrelated to the venue, a city or other government entity, or whoever else. *
Then you have the show you are buying a ticket for. This show may be a sports team, or it may be a concert or other live act. If a sports team it's probably got the same owner as the venue, but if a concert or other live act you have...
Promoters. Promoters rent the venue, pay for the show (i.e. they pay the band their fee to come play), sell the tickets, staff all the parts the venue doesn't, and pocket the difference. The promoter takes a risk, in that if they pay Major Act $1m and spend $500k on marketing/the venue/staffing and nobody shows up, they lose $1.5m. The band and venue still get paid.
The ticket platform. This platform sells the tickets for the event and adds their service fee. That service fee is generally used in part to pay the venue for the exclusive rights to sell tickets at the venue to the venue owner. That is both obviously valuable (fans can either pay your fee whatever it is or not go) and an obvious monopoly (if there were two ticket platforms selling for the same event the same seat would likely get sold twice sometimes).
Where this gets dicey: Live Nation (which owns Ticket Master) is both the biggest promoter and a ticket selling platform. Both by far. In fact they pay for exclusive rights to more than 80% of large venues. Most states only have a few venues that can do major acts (20,000+ seats), and a major act has essentially no alternative but to either play Live Nation venues, or play smaller evenues where independent promoters will pay them smaller fees.
Artists hate this system because it gouges their fans and arguably reduces their rates (there isn't a thriving market of promotors because most of them can't even use most big venues) but since Pearl Jam lost trying to break it up 30 years ago (when they were separate entities and TicketMaster had just as big a monopoly as now) they've not bothered to sue. Fans hate this system because they get gouged coming and going. It works well for Live Nation and the venues, obviously, though the venues still would be fine as they have very little competition. In my area there are two viable venues in the summer for a 25,000 person concert and one in the winter, and we're bigger than most.
Live Nation can use the vertical integration (they get both the promoter's share of the ticket revenue and the ticketing fee) to buy up most venues. And by buy up I mean either pay for exclusive contracts too, or just purchase outright.
It's been pretty clearly in violation of anti-trust laws for decades. TicketMaster before the merger and the combined entity now. I don't know how they've gotten away with it for so long, and they should undo the merger they never should have allowed to begin with.
*Unrelated but interesting: the venue also sells the rights to services inside the venue, like merchandise and, most lucratively, food and beverage. Third parties buy the rights to sell all of the food and drinks for very large sums. So a venue owner is responsible for relatively little of the work that goes on inside the venue. Someone else sets up the shows, pays for everything, sells the tickets, sells the food and drinks, etc.