Again you missed the point. The goal was to do it with ressources a lot less powerful than the players.
I'm finding this conversation tiring, so you can respond to me however you like, but I'm done.
The original poster asked for advice on how to run high level play that didn't look something like, "You open a door and you see 3 adult blue dragons."
Basically the first encounter in "Isle of the Ape" is with 60 3rd level barbarians, 60 5th level barbarians, 40 6th level barbarians, 20 8th level barbarians, 20 9th level barbarians, 4 10th level barbarians, 2 11th level barbarians, 2 12th level barbarians, 1 14th level barbarians, 4 2nd level shamans, 2 4th level shamans, 1 6th level shamans, 1 8th level shaman, and 10 18HD giant carnivorous apes. That's one encounter. They make 300 attacks during round 1 - I wonder how many groups actually rolled all three hundred d20's? The text of the adventure encourages the DM to allow these forces - a small army with 10 giant sized blood crazed (the text's description) apes - to muster precisely, unseen, unheard, undetected, and unavoidably into a perfect position to ambush the party more or less regardless of what they do up to that point. This little army of isolated primitive tribesman contains 29 name level characters, and would suffice rather well - in different garb - for the assembled Knights of the Round Table. There is this wonderfully inadvertently(?) funny notation in the text something to the effect of, "These natives are slightly different from the ones in the Monster Manual, but no great deviations have been made."
Now, I think we could pardon the neophyte DM for not really considering this assemblage when designing challenges for a party of characters based on reading the text he was given from the MM or DMG, or from thinking upon seeing this as a suggestion that this is only a little better than "three adult blue dragons in a room".