http://deepspaceindustries.com/
Cost to start mining will be astronomical but so will be the quantities mined. Asteroid mining is not that far away in time. Privatization of space industry is bringing down costs. You don't really know whether the costs will be so high that the market won't be flooded enough to keep the price of precious metals down.
Lol, this is complete bullshit and those companies are basically Buttalik Butterin IPO scams. It's such bullshit they can't even create a valid infographic of what said mining would look like. Does this look like something you're going to see anytime soon or even a valid way to mine in the first place? LOL. Let me guess, the structure on the left is a Dyson sphere they're trying to maneuver around the sun to start up the miner (which probably also mines bitcoin at the same time):