If you're taking money from X to try to push people to buy X instead of saying "our honest opinion is that Y is the best-value product and we recommend it" and putting that front and center, it's safe to say that you are manipulating people. The non-manipulative use of that real estate is showcasing high value products such that you feel it reflects well on your business to point them out. If they were organically there already, they wouldn't need to pay you.