That aluminium is widely available on earth was necessary to my point that it is trivial to find existing examples in the trillion-dollar scale.
Aluminium prices would only fall if you were selling the whole thing in one go for instant delivery — unusually for most supplies this form of delivery would be technically possible, but RFGs are normally considered "weapons" rather than "shipping". Look at how much supply has increased this century vs. price: production has seen near-continuous growth while the price has been spiky rather than a consistent downward trend, this is because aluminium is *really useful*.
Given that orbital dynamics makes it more like a months-to-years process just to get to the asteroid in the first place, who knows how long to capture it and stabilise for mining etc., and that mining itself would not be an instant process even if we happen to get a convenient pile of purely metallic (non-oxidised) rubble, it won't be all on the market for instant delivery.
So would the cost of building space elevators. I'm betting there wouldn't be a single part of society unaffected by an explosion of raw materials at much lower cost. It's just an insanely high investment cost to kick off the industrialization of space.
Besides, mining on earth has many externalities that aren't reflected in the commodity price. Some of the most brutal and inhumane conditions on earth right now are tied directly to market demand for rare or difficult to aggregate minerals. The sooner we can shut that down the sooner we can claim social progress without ten asterisks trailing it.
https://en.wikipedia.org/wiki/List_of_countries_by_aluminium... *
Calculation: http://www.wolframalpha.com/input/?i=1%20trillion%20USD%20%2...
* Old data, China has rapid growth in this sector and is now about 42 megatons/y, but that just changes the result from rounding down to 6 years to rounding up to 6 years: https://www.reuters.com/markets/commodities/china-2023-alumi...