I just use ticketmaster for music and book direct with theatres for plays and shows. I'm not sure ticketmaster is all that cheap, but I feel I know where I am with them.
Their tickets are £22.50. They have a £4 service charge per ticket and then £3 to post. I'd say it's pretty normal and that £22 per ticket is pretty cheap for a gig (although he doesn't exactly command high prices

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