Cell animation or digital, they still have to draw out every movement that their characters make.
While it's considerably harder to make a proper 3D model of a character, the work is done as soon as he's ready. After that they can just set him up to do the movements and poses that they want him to portray.
That is at least my theory. If someone around has a better idea how 3D animation works, please correct me.
I majored in Animation, and you're basically right. I mean, after a certain process you have an infinitely reusable model, resulting in cheaper sequels. Somebody builds a model, somebody adds textures to it, then somebody else adds a skeleton for animation purposes. They also add a system that can account for hundreds of facial expressions and mouth movements.
After that, it's basically ready to be used as much as needed. Animators place the character in the scene and animate it to their heart's desire. This part is much easier to do than traditional animation, but it's challenging to make it look natural. After somebody else comes along to add lights, the rendering phase begins. It can take a computer anywhere from an hour to days to render a single frame (depending on its complexity) and it isn't effortless because it requires people to constantly troubleshoot the lighting, layers, and cameras.
Traditional animation varies a LOT depending on the studio and budget. Some studios entirely ink and paint cels, some paint cels copied from cleaned-up pencil sketches, some do most of the work with a stylus on a computer, and some just go the cheap route and use Flash. But for most cases 2D animation is tedious and not a job I would want. I guess that's why so much animation is outsourced to Korea.
3D animation of the Pixar quality costs around $1,000,000 per minute of footage. 2D animation of the Disney quality costs even more. 11 minutes of "Aqua Teen Hunger Force" probably costs about $10 and a bag of marijuana.