3D printers are still very expensive. The Z Corp ZPrinter 310 plus (product page), which is an entry-level 3D printer costs you $19,900.

The new online service RapidObject enables you to print real-world 3D prototypes from your software 3D models without having to own an expensive 3D printer.
Many large companies own a 3D printer, with an on-demand service 3D printing service smaller companies can also benefit from this cool new technology.

RapidObject uses the 3D printers from Contex (product page). To 3D print small objects the service charges about 100 Euro.

See an example of a printed spark plug below. RapidObject is a service by German based Firma RT Reprotechnik GmbH. The 3D print service will launch on September 28th (in Germany) and will be available internationally. The English language site will launch mid-October.
See also the RapidObject site.