I think that's entering an area of ad ethics. Yet, its an ethical violation that companies like Google make today. If I search for "Wealthfront", I get an ad for Wealthfront, Betterment, and TDAmeritrade, in that order, before an organic result for Wealthfront. If Wealthfront didn't pay up, even though it is _obvious_ what I am looking for, the result I am looking would be buried. That's a protection racket.

Rank-based advertising, like in search results, is fundamentally unethical. To do it ethically would require perfect comprehension of what the searcher is seeking, so that you can prioritize organic, helpful results. Google never prioritizes organic results.