Ok, I'll defend the guy.
$50 says he's no more than 10ft/3m off the ground. I can get you 30 equally impressive but still perfectly safe shots in a 1 hour outing.
It's the third pic in the set that gives it away. It's from a different angle, meaning the cameraman is several steps to the right from where the other shots were taken. Look at the bush that appears to be near the base of the tree, and the other tree that takes up the right hand side of the frame. There's apparently allot more room to move around up there than the first two pics seem to imply, and likely only a short drop to a steep but relatively safe incline.
As far as the tree's strength is concerned, look at the trunk diameter relative to his foot. It's as thick as his foot is long. Plenty strong enough to hold his weight.
I don't have the photos any more, and not allot of friends who can keep up with me on the trail now days, but I've taken similar shots in the past from little more than an arm's length away that make someone appear 20ft/6m up a rock face when in reality they're standing next to the cliff on a rock that's no more than knee high.