The process of making a statue like this is exhibited in another instructable (an Alien Queen), but in short, this is the process:
I made a skeleton/frame out of foam boards, cut up into various shapes and hot-glued together to fill out the basic shape. That frame was then covered with tape to fill out the shape. I then put on a layer or two of plaster strips, dipped in water and then laid on top. After it dried, I smoothed it out a bit with some plaster (of Paris) mixed with water to a thick milky consistency painted on top.
A few extra details: the areas around the eyes were shaped with some clay on top, the claws and teeth made out of clay, and the eyeballs a half of a ping pong ball. Then spray painted the whole thing. A support stand was made out of foam board.
The whole thing was 6 feet long and weighed about 12 pounds. Estimated budget of about $25 (most of that going to plaster strips and foam boards).