In Marc-Uwe Kling's Quality Land novel [1], the absence of purchasing power resulting from AIs having taken over, is mitigated by shopping robots buying random useless stuff.
[1] https://www.amazon.com/Qualityland-Marc-Uwe-Kling/dp/1538732...
[1] https://www.amazon.com/Qualityland-Marc-Uwe-Kling/dp/1538732...
The novel is a bit of a dark comedy sci-fi. And even though many details are surprisingly accurate (for a story written a decade ago) robots buying crap produced by robots is IMO meant to illustrate an absurd racket to inflate demand.