Facebook is testing a new feature named Highlight.
The basic concept is that you have an option to pay a small amount to highlight a post of yours to your contacts.
USD 2 seems to be what they are charging right now as per Stuff.co.nz.
This seems like an interesting idea that could generate significant revenue for the company if it becomes popular. But it can also cause a lot of friction amongst its user base which might get annoyed through continues highlights on their streams.
Facebook is currently testing this feature with a limited number of users on their network.