I think it's instructive to look at how Yelp does it. There is no pay-to-delete button. There are however ways to have non-factual, incorrect, offensive or a myriad of other types of posts removed. How a review is judged as violating policy is an internal decision. Which reviews are surfaced on the front page or how the "average" review is determined or slew of other details that affect how a restaurant or company looks are are also under the control of yelp/glassdoor.

There are enough ways to put the thumb on the scale that you can honestly say that you don't have a delete bad review button, yet money can still strongly influence how positive or negative an org looks on a review site.