The one biggest factor in slow ticket sales is that they put the tickets on sale damn near a year ahead of the shows. Six months is usually the longest. I guess it's normal for Europe... but here in the states, to get us to plan something out that far in advance is a pain in the ass. Everybody I know is like, "I'll see what tickets are left once the show gets closer."
And then, for me, personally, and I can't be the only one... since I have to travel for a show, I can't plan anything yet because the airline I use isn't even showing fares that far in advance. Remember, Eurofolk, we don't have a real train system here.
And then, the final kicker, is that if I can't plan in advance, and who knows if I can even get the days off of work, why in the hell am I going to spend a hundred bucks on a pit ticket that, if I'm not able to make it to the show, I can't transfer or resell? Again, I appreciate the anti-scalper stance of Maiden... but... I'm just supposed to eat the hundred bucks?
So, to sum up... I don't think slow sales have anything to do with a decline of Maiden, I think they have to do with bad tour planning, in regards to announcement timing and ticket on-sale dates. Waaaay too far off for most Americans to be thinking about.
And, they didn't book Denver, which totally sucks.