I think the main issue is that Amazon doesn't have to boost the sales of actual goods if they can make it up in ad fees. And that situation is only stable if f

I think the main issue is that Amazon doesn't have to boost the sales of actual goods if they can make it up in ad fees. And that situation is only stable if for some reason the vendors have to be on your site and keep advertising anyway, which is the hallmark of a monopoly adjacent situation.