Metallurgical engineer here. One thing I never see talked about on this topic is how astreoids don’t have nearly the mechanisms for concentrating matals into ores like planetary bodies do.

So while there may be a higher proportion of, say, iridium on an asteroid than the average of Earth, it is pretty homogenous. You would have to refine the whole thing to get a little bit of iridium. On Earth, it may be more rare on average, but Earth also concentrates metals into ores via heat, gravity and water action so that you can mine a small area to get what your want economically.

Metal meteoroids are mostly iron, which is cheap on Earth and of little use in space. Aluminum, which is useful in space, is one of the most common elements on Earth and even higher on the Moon, but it’s only economically mined in tropical soil that had ages of water erosion. Titanium, different process but similar story.

Given the economics of getting to where you want to mine, mining a non-concentrated rock, and then transporting it back to Earth’s for sale I just didn’t see any path for mining asteroids.

Once there’s is an established human presence in space, there might be a reason to mine organics (CHON) but that is not now and not what people think of when they tout asteroid mining.