In a way, I do have some sympathy for those people who are shelling out hundreds (and thousands!) of pounds for gig tickets to see their favourite artists. However, I can see why Viagogo and Seatwave operate these ticket websites if desperate fans are willing to pay these prices and if they do so, they really shouldn't complain as long as they get what they want to pay for. Quite simply, if they are too expensive, then why do the fans feel honour-bound to buy them?
As someone who does a bit of gig reviewing, it has been a little while since I have had to buy a music ticket, but I would certainly get fed up if I had to pay so much for an evening's entertainment. Having said that, the last ticket I bought was from a tout in Brixton for a drum and bass gig, for which I only got shafted an extra tenner for a ticket that was originally an early-bird ticket with a slightly lower price.
If you can't get tickets, it just wasn't meant to be and if the band is popular, console yourself with the fact that there will be other opportunities to see them. Otherwise, you are only a fool to yourself if you want to pay hundreds of pounds for one off shows and then complain about it afterwards.