I saw the prices on JDS Offroad. About $700 for a set. I think it costs about an average of $125 for a traditional beadlocked wheel. The Hummer beadlocks, if I'm correct, use a run flat nylon lining along with more traditional beadlocks on both sides. Not sure about that though, and I think you have to get them custom drilled to fit your bolt pattern. Those are about $250 a piece if I remember correctly.
I might try these out along with some steelies. Another pro for the system is that if the wheel is heavily damaged, is that you can buy another wheel to replace it for cheap. I also wonder myself why it's not that popular in the states. The price may be a factor, but also you would expect to see the hardcore rock crawler types clinging to this type of stuff. Instead, I tend to see the more traditional beadlocks on these built rigs.