if agi is commoditized and labor is useless, what does anyone need capital for? paying ad time on monopolized social media channels?

Commoditized doesn't mean 0 capex. Literal commodities can in fact be very capital intensive (ex. offshore oil rigs).

In this case, you need capital to stockpile the GPUs.

I've put some of my savings in commodities (mines, etc).....

If ASI and the ability to build robots becomes generally available and virtually free (and if the exponential growth stops), the things that retain their value will be land and raw materials (including raw materials that contain energy).

For the physical infrastructure that the AGI (and world population) uses. Capital will still be needed to purchase finite land and resources even if all labour (physical and services) is replaced.

Labor will never become worthless until you have physical robots with AGI and the dexterity to do what an average human can.

How many months is that moat going to hold? More than 12, probably. More than 120? I doubt it. https://www.youtube.com/watch?v=bUrLuUxv9gE

Probably 10 years once we get to AGI but we are not there and there is no guarantee we will get there.