The real comparison is in airline tickets. If we can have a robust market in airline tickets, with multiple sites competing to sell you tickets, and with only marginal (if any) service fees, then you would expect the same would be possible for rock concerts. For a closer analog, I've seen movies where I bought the tickets online (via Moviefone) and picked them up at the theater. The service fee is something like $1/ticket. That sounds like a reasonable "convenience fee". Anything beyond that is profiteering.