Adam Mann of Wired describes the interesting plans of Deep Space Industries, working on the idea of how to make money from asteroid mining: "New Asteroid Mining Company Aims to Manufacture Products in Space".
A year later, DSI wants to launch larger spacecraft called DragonFlies that can make a round-trip journey to an asteroid and bring back samples. They estimate the trip will take two to four years and can return as much as 70 kg (150 lbs) of asteroid material to Earth orbit. DSI has patented technology they claim can extract precious metals from raw asteroid material and build it into parts with a 3-D printer.
The article makes it sound like they're trying to finance space operations by selling tchochkes.
Real manufacturing of most light-yet-expensive items today involves layers upon layers of different substances fitted together into complicated objects. That kind of assembly and separate refining of hundreds of substances on an asteroid would be a true engineering challenge. It's easy to see that the ability to manufacture parts in space at large scale would be much more valuable for use in space than back on Earth.