space - Ticketmaster, Seatgeek, Stubhub, Vivid Seats, etc. They aren't going to get away with charging fees that the market won't bear with that kind of competition.
But they do provide a robust platform where people can safely and securely exchange after market tickets. That provides value both for a buyer who is looking to buy tickets to an event and to sellers who want to sell some tickets. They facilitate the exchange seamlessly and provide protections and payment services for both the buyers and the sellers. You aren't going to get that from some guy holding tickets up outside a stadium.