I believe that when someone "unlocks" an ultimate weapon, Gantz makes a couple of copies. If you think about it, there were at least 2 bikes and 5 swords. A well-organized team (like the one Kurono built) would distribute the weapons based on skill (I doubt a sniper would need a sword, for example). The bike can carry both a driver and a shooter. So, at least 7 people would be utilizing the ultimate equipment. I also believe that the advanced cloaking and radar were earned.
And the bike? I bet it has many secrets yet to be discovered, just like the guns and the control pad had.