Agreed. There are a dozen unsolved problems in the way, and uncounted billions of dollars to get there. And it will always, always be cheaper to create a space-based industrial complex than to bring any of the wealth down to earth. So what's the point.
Space tourism, cheap comms, sell the platforms to the military, space solar, be the first to get your DNA all over a new planet.
Although if it's true that it's cheaper to get the resources on earth than to bring them down from space then it does put a big hole in their current business plan.
Its more efficient to use them up there in space, than to drop them into a hole (down the gravity well).
Think of it: the entire space-based mining industry needs equipment, parts, rockets, everything. Why make them down on earth? Make them in orbit, or better yet right there at the mine site.
The first decade of mine production would sensibly go toward more mining infrastructure. That's the most expensive equipment on earth - why send platinum down the gravity well to be made into pop cans, when you can sell it back to the mining concerns for making more mining equipment.
Then you start to question the whole point. Other than moving imaginary numbers (dollars) from one column to another, what's the point.
This isn't as far fetched as it first seems. With Elon Musk's rockets they can get satellites to space cheaply, then map the asteroids with cameras, then send robotic satellites out to mine and send packages back to earth, or keep in space. They can create the satellites in space or on the moon in a kinematic self replicating manner.
Easy to say "send robotic satellites out to mine". How does that work? Six or seven insoluble problems there. How to get the robots a billion feet to the mine site? How to concentrate enough energy to actually do any effective mining? Where does the energy come from? You didn't drag a gas can that whole way.
Spare parts - the store is a billion feet away. How to install them - robots? Who fixes the robots? How many robots does it take to keep the whole machine running? It takes 70 tents to get to the top of Mt Everest - a trivial endeavor in comparison. 70 tents - to get 1 tent to the last base camp with oxygen bottles enough to make the final ascent. All the other tents are to hold the tents and oxygen bottles to get you to the next base camp.
What about dust? Mining is dirty. The dust isn't going to 'blow away', or even settle. Its just going to collect in an ever-denser fog directly around the mining site. Grit particles from sand-sized down to microscopic. Getting into everything. Clogging up every joint and piston. Got to address that.
How to boost the ore back to earth? Or smelt in on-site - with what energy? Maybe drag the asteroid back to earth - again, with what energy? Maybe just drag it halfway back (or 2/3?) - now the ore/spare parts trip is half as long. Huge optimization problem there - must be solved.
Ok, solve all that - robots repairing robots, parts shuttling back and forth, smelting and hauling... finally we have pure metal in orbit around Earth. Yay! Oh...how do we get it down? Drop it in a lake? Not my lake! Make landers out of it? With what factories? Another entire industry just to get the damned stuff on the ground so we can make those palladium pop cans or whatever.
Each problem is an entire industry, requiring problem solving on a stellar scale. Lots of mistakes, lots of money down the drain, all for metal that we already have lots of a few thousand feet away already - in the earth's core.
Hey! Why not just do deep-core mining - the robots are only a few milliseconds away, not millions. The ore need only be hauled feet, not parsecs. Spare parts are down the road.
Anyway, yes, its completely far-fetched to do asteroid mining. All the engineering we have done as a race is small compared to the obstacles to be overcome. The concentrated effort requires a century of focus and probably trillions of dollars or rupees or whatever.
You've made a lot of arguments along the line of "it's difficult difficult difficult" but haven't given a specific example of why it can't be done. What do you think of self-driving cars? That was difficult too, and basically the same kind of problem (autonomous navigation). In fact, it's probably easier than robocars since it's much emptier up there.
The hardest part is building satellites in space, which they haven't said they will do (but I think is possible, as described in the 1980 study).
Start from fundamentals I guess. One hard issue is energy density. Boosting significant energy to distant reaches of the solar system is prohibitively expensive (we've never done it in human history). Generating it there is unlikely - the solar energy density is miniscule because of the distance (asteroid belt is 3 times more distant than earth; energy density is 1/9th per square).
