An open Source fully 3D printable camera lens for Canon EF has been developed by Photographer Felix Steele.
www.3diest.com
It is much very much cheaper than any normal lenses and will cost you around 15$ to make, this complete project has been named by Steele "Pixels and Prisms".
www.3diest.com
The Pixels and Prisms are 163mm f/2.5 telephoto lenses and are designed to be a fully customizable optical system, Low-cost, and open source. It's a great alternative to commercial lenses that can be made using 3D printing.