in terms of cash value, it sounds like a fair trade. So it's not like you're getting a bum deal or anything.
But in terms of lasting gameplay appeal ... I really feel like Funhouse gets old pretty quick, because of the limited ruleset. You just end up putting Rudy to sleep and waking him up over and over and that's pretty much it. It's a lot of fun for casual players and kids, though. Rudy is my favorite toy in pinball.
Xenon is a fun game with great art, but it's really not particularly deep, either. I think both of these games will get boring if you play them very much.
With STTNG, there are like 14 different modes to play -- the seven main ones, the three side missions, video mode, warp 9.9, the final frontier, and borg multiball. And in terms of scoring, it's a fun bit of strategy to try to pick between Borg Multiball infinitely-buildable jackpots, Final Frontier artifacts, and the Super Spinner Stack strategy. My brother and I are constantly arguing over which one is best (it really depends on your skill level and how the game is set up...)
anyway, IMO it's a fair trade money-wise but a bit of a loss fun-wise.