I've just booked tickets for The Blue Nile at Somerset House on Sunday evening and it's the usual rip-off: on top of the £2.75 booking fee it costs £2.50 to print out the tickets - the same as having them posted to me, but I pay for the printing. And the ticket isn't the usual small ticket where you could fit two on one sheet of A4; it's padded out with adverts for Ticketmaster and the venue that I'm instructed not to skip printing, because I have to present the 'entire page' at the venue. The ticket is in colour; this can't be a counterfeit prevention measure because every printer will print it differently, so that raises the cost of printing from a mono page. It's the barcode that matters and that's on twice - fair enough, in case one gets creased. And there may be a good legal reason for putting the terms and conditions on there. But without the ads, you would still get two tickets on one sheet of paper - and singletons would still save on the ink.
Of course it's only one sheet of paper, and half a page of ink. But multiply that by 3,500 people at the gig, and then ten gigs in the series and hundreds of events a month. What a huge waste of resources.