Of course, there have to be other jobs available! If there are none because machines make everything, then you might have a problem.

Yes, mightn't you. That's end game capitalism. At that point all the available capital is held by perhaps 100 people in the world. The rest have nothing and no money to buy widgets. The environment is destroyed and the planet becomes unlivable.
Those 100 people take all the money in the world and blast off to their 4 star resort on Mars to escape the apocalypse.
Good coffee, good weed, and time on my hands...