You see, $120 doesn't entitle you to sell whatever you make with the engine. From what I've read, this only gives you access to the source code. It's still up to them if they want to publish your work, or not, and I beleive there are some addition royalities involved after that.
Also I've seen Tribes2, and it's not that impressive. Maybe the game itself isn't a very good demostration of the engine? But this doesn't really make any difference, because it's not access to an engine that we need.
What we really need is access to the engine's creator. We have some new ideas that probly won't be supported by whatever engine we choise. We need the extra flexablity of working with the engine's creators to make these things possible.