This is the one area where EBay can get nasty - mainly because obviously the even has already taken place and now the tickets are worthless.
It is difficult because on the one hand you have been mis-sold tickets, there is no doubt about that.
The price means nothing, the description is not what was sent.
So I would say there is an immediate claim for "not as advertised".
However the tickets were used.
I think I would contact the seller, explain once more and ask them to refund some of the cost back.
Yes you got tickets, however they were not as represented.
If that gets you nowhere then I think I would be tempted to raise a dispute.