From my understanding this "treasure" is in like a bronze chest and inside the chest it has all kinds of intrinsic valuables like coins, gems, etc. Just the chest alone would be worth a nice sum.
The key about this whole thing is the guy didn't bury it. He was very smart about this. And the reason why he didn't bury it is because if someone found it and had to dig it up, technically it would property of the National Parks and Services Dept. Someone else maybe with more insight can elaborate more here, but NPS has the rights to anything that's ever technically dug up in a designated National Park.
However, if he just left it "above ground", that includes above ground inside a cave, and someone happens to be so fortunate to find it while searching for it or just someone passing by, then they could rightfully claim it.
Really cool how he thought all this out. He did it so people would get back into searching maps and exploring the wilderness in National Parks and trying to figure out where it is. He takes a great pleasure in seeing and reading about all the treasure hunters.
Side note: A customer of mine took his family camping in one of the National Parks in that area (can't remember which one) and each night before he, his wife, and two boys would go to bed, they would read the poem all together and he would search the map of the area where they would hike and tell his boys in a serious tone that "he knows where the treasure is!" Then the next day they would all go out and all search for it following the map and clues, and of course come up empty handed, but the kids took a real joy knowing that they were in search of this real treasure.
It's out there somewhere...