Like agriculture. That market has grown significantly through time, even though it's shrunk dramatically as a % of GDP.
AI cannot make money as an alternative to large scale employment, because essentially all the clients of those AI businesses will see demand for their products and services collapse. AI bots don’t go to In-N-Out Burger or Disneyland.
Anything else is fantasy maths, albeit commonplace fantasy in the AI industry at the moment.
Here you are talking about a shift taking employment out of the economy full stop — taking the money that would have gone to "a good chunk of labor", to use your words, and giving it to AI firms.
You are necessarily talking about job elimination en masse — it's the only way this hypothetical source of money is available.
If you take labour out of the market, en masse, you cause demand to collapse. Because they won't be economically active!
New industry after new industry has been created over the past 100 years. It's difficult to believe that all of a sudden that stops.