The airship set is currently $9. A little steep, but so are all of the SimCity downloadables (amusement park set for $10?!)
It’s really neat though too, and therefore tempting.
My largest complaint about SimCity continues to be that the city plot areas are a bit too small to really see your city grow into something amazing. Sure you can claim all the plots in the region and have some super-region but you also have to try and make each city independent… or maybe I’m just doing it wrong.