I also ask LLMs for product recomendations. But the moment I suspect they are hidding the best items (not paying for the ad) to push the second best (not even talking about pushing shit as good products because they pay more) is the moment the LLM loses its value as recomender.
If they want to capture some of the value they provide, they should do it the standard fashion where they directly capture value from me by having me pay.