I agree with a small 10 to 15 % mark up, after all, you missed out on pre sales and normal sale….
Some English Soccer Clubs have a secure method in which to exchange tickets, all it costs is the yearly membership to the club (which usually includes a fan pack of some sort with "stuff"), no mark up on the tickets, at least I don't think there is, perhaps some one in England can confirm that. If Ticketmaster truly cared about giving a secure platform to exchange tickets, they should look at their model…..Arsenal rocks BTW …yea yea I know, no need to say any more….