3D printing is a relatively new manufacturing process that is being used more and more every day. Just recently a 3D printed part made by BAE systems was used in a RAF fighter jet (http://www.baesystems.com/article/BAES_164442/3d-printed-metal-part-flown-for-first-time-on-uk-fighter-jet?) This blog post talked about how much it actually costs to 3D print parts. Now the machinery itself is extremely expensive. Even a low-qualilty printer that can only print using cheap thermoplastic materials will cost you a few thousand dollars. But when you spent the money you can create metal parts that are very high quality. But once you have the printer there are number of factors you have to take into account when calculating cost. The first being how much space the part takes up in the printer. This dictates how many parts you can make at once. You also need to know the cost of the material/powder you are using and the volume you need. The printer itself uses electricity to run and has a number of components that need to be serviced and eventually replaced. These operating costs also have to be taken into account.
The Blog Post: How much does it cost when you 3D print a thousand different parts all at once? by Raphael, 10/3/14.