Want to send a Facebook message to a person who is not your Facebook friend? Pay up.  Facebook on Thursday starts testing if it can monetize and cut spam at the same time by asking you to pay to ensure the recipient sees it.

Facebook’s also changing everyone’s privacy settings into dynamic filters that let “relevant” messages through. Facebook says the changes are primarily designed to let Facebook users who already know each other make sure their missives connect. But the most interesting part of the move is what the social network is calling a “a small experiment to test the usefulness of economic signals.”

The feature will be available only to limited users in U.S. Facebook isn’t spelling out the cost publicly, but report suggests that it will start at a dollar a message, and Facebook may change the fee over time. Facebook will only allow users to receive a single paid message per week. But users can’t opt not to receive paid messages.