This is quoted directly from the Orange County Register article:
Indiana Jones Adventure was among the most innovative attractions ever created when it opened in 1995: It was the first to put an independently moving platform that holds the passengers, like the Star Tours' simulator, on top of a vehicle that runs along a track.
Today, the Jeep-journey ride ranks as the second-most expensive attraction to maintain in the Disneyland Resort, behind California Screamin' at Disney California Adventure, said Jeff Corder, Disney senior manager of engineering services.
Now I thoroughly enjoy California Screamin', folks, but it is still a rollercoaster. No AA's, no special effects, just cars and tracks (and a launcher, OK). How can a rollercoaster cost Disney more to maintain than a technologically-complex attraction like Indiana Jones?