Seller agrees to sell ticket at PRICE. Monopoly intermediate provider sells it at $PRICE+$markup. Monopoly intermediate provider sells it to a reseller, which artificially limits the supply available to buyers at any given moment. Buyers have to go to resellers, who then pay $markup2 back to the monopoly provider to transfer the ticket to the ultimate buyer. This may even repeat several times, resulting in the monopoly provider reaping more in markup fees than the seller receives for the actual product.
Original seller is free to sell it with the stipulation that original buyer is the only person that can use the ticket.
However, entertainers have an image problem that conflicts with the desire to maximize profit. Entertainers are often times in the business of appealing to the broader public. But if they restrict their ticket sales to the highest bidder, then the broader public's appeal is limited.
Having a third party engage in the price discrimination allows the entertainer's image to remain intact, while also collecting higher prices (perhaps not from the ticket sales directly, but the third party willing to pay more for the entertainer if the entertainer allows them to resell tickets).
