How are businesses going to get money if there are no humans that are able to pay for goods?

Lots of us are not cut out for blue collar work.

> How are businesses going to get money if there are no humans that are able to pay for goods?

By transacting with other businesses. In theory comparative advantage will always ensure that some degree of trade takes place between completely automated enterprises and comparatively inefficient human labor; in practice the utility an AI could derive from these transactions might not be worth it for either party—the AI because the utility is so minimal, and the humans because the transactions cannot sustain their needs. This gets even more fraught if we assume an AGI takes control before cheaply available space flight, because at a certain point having insufficiently productive humans living on any area of sea or land becomes less efficient than replacing the humans with automatons (particularly when you account for the risk of their behaving in unexpected ways).

Some humans will be rich and they'll buy things. For example those humans who own AI or fabs. And those humans, who serve to them (assuming that there will be services not replaced by AI, for example prostitution), will also buy things.

If 99.99% of other humans will become poor and eventually die, it certainly will change economy a lot.

There is an amount of people who own, well, in the past we could say "means of production" but let's not. So, they own the physical capital and AI worker-robots, and this combination produces various goods for human use. So they (the people who own that stuff) trade those goods between each other since nobody owns the full range of production chains.

The people who used to be hired workers? Eh, they still own their ability to work (which is now completely useless in the market economy) and nothing much more so... well, they can go and sleep under the bridge or go extinct or do whatever else peacefully, as long as they don't try to trespass on the private property, sanctity and inviolability of which is obviously crucial for the societal harmony.

So yeah, the global population would probably shrink down to something in the hundreds millions or so in the end, and ironically, the economy may very well end up being self-sustainable and environmentally green and all that nice stuff since it won't have to support the life standards of ~10 billions, although the process of getting there could be quite tumultous.

As long as someone else is still paying their employees, it’s all good.