Most of those auctions do say that the proceeds are going to the charity. Whilst I disapprove of anyone cashing in, there might be some genuine sellers amongst that lot who need to sell on tickets.
I think anyone who has gone out and bought tickets purely with a view to reselling them is a complete git... but I think that about people who do it for any concert or event.
Once again though, as long as people are prepared to pay them, they will continue to thrive.