Yesterday I bought a ticket at >2x face value for a concert on Monday. That's value for me - I'd like to be able to go to things without having to plan my life months in advance, and I'm willing to pay for the privilege.
Supply isn't set in stone. If scalpers buy up tickets early on then they take on the risk that a show won't sell out, and that allows the promoters to move to a bigger venue (as happened in this case), add more nights, or even raise prices. So the promoter benefits too.
It's no different from any other middleman: find someone who's selling at price x, find someone who's buying at y > x, connect them together and take your cut. Which is what makes capitalism works.
You're missing the negative externality: the person who couldn't get in because you're paying some scalping dick. And let's not forget the performers, who are interested in performing for their best fans, and who try to set ticket prices accordingly.
Supply isn't set in stone. If scalpers buy up tickets early on then they take on the risk that a show won't sell out, and that allows the promoters to move to a bigger venue (as happened in this case), add more nights, or even raise prices. So the promoter benefits too.
It's no different from any other middleman: find someone who's selling at price x, find someone who's buying at y > x, connect them together and take your cut. Which is what makes capitalism works.