system
Given the following post, respond as if you're commenting on Reddit:
human
What makes mining asteroids so potentially profitable?

To add to the question, what rocks/ore/minerals within the asteroid are so valuable and who on earth (literally!) would pay big bucks for it?
gpt
Forget the huge numbers you see quoted sometimes.

A cubic kilometer of random rock on Earth contains of the order of 10 tonnes of gold with a market value of ~$500 million. How much does it cost to buy such a cubic kilometer of random rock? Basically nothing if the surface is not useful for other means. So why doesn't everyone buy some land in the desert? Because extracting the 10 tonnes of gold out of the billions of tonnes of other stuff needs much more than $500 billion.

"This asteroid is worth X!" uses the same misleading calculation. They just consider how much gold and other rare elements are in there, multiply it by the current market price, and announce that as "value" of the asteroid. Take a big asteroid and you get a truly astronomical value. That doesn't mean you can just go there and pick up the gold. If filtering through the whole asteroid and sending stuff back takes more than you can get from selling it then the asteroid has an effective value of zero.

To make it worse: These numbers can sometimes exceed the global market for the material. If you would have 10 million tonnes of gold you wouldn't have a million times the value of 10 tonnes of gold. If you would try to sell any relevant fraction of that the price would drop a lot because of the large supply.