With eBay the seller also has to deliver in a timely fashion. You're right, if they fail then the best that happens is you get your money back, but you find out reasonably quickly whether or not they're going to perform, and there's never any confusion about whether or not the transaction has completed.

So a big part of this problem is that StubHub is letting sellers cheat buyers out of massive appreciation by not giving them a reasonably deadline for delivery, nor penalizing the sellers for failing to perform.

The potential costs to correct the situation don't have to be an issue, because StubHub could conceivably push those costs onto the seller trying (and in this case apparently succeeding!) to cheat the system. They could write their seller contract to state that the seller is responsible for all costs borne by StubHub acquiring replacement tickets, and that would remove their incentive to pull stunts like this.

As others have mentioned, in many cases the seller doesn't physically have the tickets at the time of sale, and might only get them a few days before the game. Ticketmaster cooperates with venues to do this to -- dum dum dum -- avoid ticket resale. That's the problem.

If they're going to support such tickets then they need some big "seriously, deliver what you sold" penalties for bad sellers.