The scalper is trading volatility (they may or may not sell the ticket for a higher price) for the opportunity of a return. The venue is getting the opposite side of the deal. Guaranteed income now.
> if, on average, scalpers didn't get their payout, then they wouldn't take the risk
The point is they can get their pay-out while the venue/artist and consumers win. Scalper gets paid. Venue and artist get stability. Consumer who buys from the scalper gets availability. And the other 90% of consumers get cheaper prices.