most companies don't use 3D printers. Most of them use casting dies. First, a sculptor makes a detailed model. Then they decide where to cut the model in order to make the cleanest cast possible. After that, the pieces are sent to another master-sculptor who cuts the "negative" of the model/pieces into the casting die. (this is usually done in two separate halves, but sometimes more). The two halves are then strapped together and the medium (plastic, metal, resin, etc), is poured into the mould. After it cools off/dries, the mould is cracked open the pieces removed,... then the process is repeated over and over again.
It isn't cost effective to do this unless you plan on making multiple copies for sale to help recover the cost. Your average casting die runs between $10,000 - $300,000 to produce. You'd be better off just hiring professional sculptor to make you a one-off piece.
