They're definitely not cheap. Resources are so difficult to come by here, and the supply is nowhere near as high as the demand. We're a little better off, since most of the local kedan would rather sell to a foreigner, but...

[... she's been working fourteen hour days (which is quite the shocking change from her life in Republic City) just to cover the costs.]

And yes, they take fuel cells. Some work on a solar battery - usually smaller vehicles, and they can't go as fast - but some work on hydrocarbon fuels. I think they must get it from the mainland.