To start building a model from my 3D file, the design is built up, one layer at a time, from stainless steel powder held in place by a laser-activated binder. You can see the layering on the finished pieces; each layer is .004" to .007" thick.
Here are the folks who make the system for printing in steel powder, then putting the result in a molten bronze bath to make the result more solid. Unfortunately, I can't find a price, but I gather it's in the range of a high-end home business.
While I'm not exactly in the market myself, I'm intrigued by the way technology has been making it more possible for people to have their own businesses, including bookkeeping software, ebay, embrodery machines, and now this.