All of the asteroid plays have so far been private companies, so their promises are light on the detail required of those going to the public for money.
This week, astrophysics researcher at Liverpool John Moores University and Asteroid Mining consultant Amanda Jane Hughes described in The Conversation what it might take for her employer to get to the mining stage.
As usual, the key part is finding a deposit.
That can be done theoretically by pointing a telescope at all of the 17,000 near-earth asteroids floating about, Hughes said, with the going estimate of a contained-metal value of US$1 billion needed to make the whole enterprise worthwhile.
"In order to satisfy this requirement, the asteroid must be more than 1km in diameter, contain more than 10 parts per million of platinum and have a velocity relative to the speed of the Earth of less than 4.5 metres per second," she said.
"… We can assume that 4% of near-Earth asteroids are also metallic. Taking into account this and other probabilities, we are left with only 10 asteroids that are - theoretically - economically worthwhile and practically feasible to mine."
So far, not that different to the likelihood of someone finding another Bingham Canyon in a nice jurisdiction.
But there are other complications, like getting a drill rig up to an asteroid (sorry, a probe): "This would be an incredibly ambitious feat of engineering that can not be underestimated, with many unanswered questions and unknown timescales at this early stage".
Hughes said even if all this was managed and an economic resource was found, there are also questions over who gets dibs.
"There are concerns that the situation could become the new Wild West, with a lack of laws leading to disputes over who has the rights to mine a particular asteroid," she said.
"There is no mechanism currently in place to adjudicate such claims, and the legal landscape is complex."
Judging by Simandou and the Democratic Republic of Congo right now this would not be an unfamiliar scenario to anyone vaguely aware of the resources world.