How is anything done by Ticketmaster and Stubhub not legitimized scalping at its worst and not already disbanded by congress? It's so rampant Ticketmaster doesn't even pretend anymore and just charges "market adjusted" prices to scalp directly themselves now to cut out most of the middle-man scalpers.
Because the artists are all in favour of it. Ticketmaster et al are in the business of reputation laundering. If the artists sold tickets directly at market clearing prices then fans would be livid at the level of greed on display.
By using Ticketmaster as an intermediary, artists are able to put artificial below-market prices on the tickets but then sell them at inflated prices, while deflecting fans' anger to the middle man. Ticketmaster, in turn, pays the artists a kickback and everybody wins (except the fans).
If they are gambling that the ticket will be worth more in the future (if it was worth more today, it would have been bought by a real customer), they could make millions, or lose everything like Zillow. Guessing what a volatile item will be worth in a month isn't all fun and games
They kinda have control of the supply of goods too though - running the main resale marketplace.
When there is an excess of tickets, they can make sure that their own stock sells before random fans tickets ('I'm sorry, nobody bought the ticket you listed for sale, and now the event is over').