Not to brag, but I've done one of these already - I climbed the mountain overlooking Macchu Picchu about six years ago. Yeah, it's dangerous; at some points, the stairs were only 2 feet wide, with a 500-foot drop right beside me. But it's not all that difficult, because the steps are still in pretty good shape, and it's a rather short climb - it took me 45 minutes on the way up, and 35 minutes on the way down. Any reasonably-healthy person could do it, as long as you watch where you step.
In my opinion, it's the longer treks that are more dangerous, because you can get lost, run out of water, die of exposure, etc. But in these hikes, the threat of death is a little more, shall we say,
immediate. ;-)
Anyways, just thought I'd toss my $0.02 in, as someone who was once lucky enough to climb above the clouds.