That's because reserves are what matters. I don't care if there's billions of tons of lithium at the bottom of the Marianas Trench, nobody's ever going to go get it because it's too dangerous, difficult, and expensive. The same thing with space mining. Nobody's going to go mine asteroids because it's stupidly expensive. For all intents and purposes, if we can't get to it, it doesn't exist.

And let's not forget about all the problems that "innovative" methods of oil extraction such as fracking have created, over and above the fact that it's provided more oil to burn. Lithium mining itself is already an environmental disaster, and it seems highly unlikely that increased demand for the product is going to improve the environmental impact of extracting it. You know, tragedy of the commons and all. The fact that "peak oil" came and went is not a capitalist success story.

Not at all. If there were billions of dollars worth of whatever on the bottom of the Mariana trench, people would build advanced technology to extract these billions, without any further incentives than the market demand.

A comparable case in point: commercial space launch companies. Arguably, commercial large-scale aviation, too.

Well, that brings us back to earlier in the thread.

It's not only about money-expensive. If it gets more energy-expensive to produce/store/route/... energy than the amount of energy we end up with in the end, the game is over.

So, in practice, there are limits to reserves. There is, of course, the possibility that these limits can change with new technologies, which in turn depends on money-cost as you mention.

You seem not to understand what "reserves" actually means.

It does not exclude easily accessible material. It only excludes material not assessed yet because there has been no need to, as existing reserves will last more than long enough to perform further surveys.