The 2012 Olympics, which were pitched at a cost of under three billion, will now cost another billion on top of the last estimate of about nine and a half... it turns out that the money raised by selling the land after the event, was based on prices continuing to rise by 20% per annum for another twenty years. They've now admitted that this was an insanely overoptimistic assumption, and reduced their expected return accordingly. (Link here
Now I was one of those delighted to hear we were bididng for, and that we won, the right to host these games. But at ten billion pounds, I think the time's come to hand them back - no amount of international prestige is worth this much.