There are ten organic positions on a page of Google results and three in the map pack. That is the entire inventory.
When one agency represents four
aesthetic clinics all targeting the same treatments, it is not running four independent campaigns. It is allocating a fixed number of positions between four businesses that are paying it to beat each other.
Someone gets position one. Someone gets position seven. The agency decides which, and it has an obvious commercial incentive to favour whoever pays the most. The clinic in position seven is never told that decision was made, or that it was made by the company it is paying.