Facebook is dabbling with charging members as much as $100 to get messages to the inboxes of strangers such as social network co-founder and chief Mark Zuckerberg.
"We are testing some extreme price points to see what works to filter spam," Facebook said on Friday in response to an inquiry regarding the costly delivery fees.
In December, Facebook began testing the feasibility of charging to guarantee that messages from strangers make it into inboxes of intended recipients.
At its launch, the Facebook Messages test, limited to the United States, let a sender pay a dollar to make sure an electronic missive is routed to someone's "inbox" even when the person is not in their circle of friends.
In a spin revealed by Mashable and other technology news websites, the test includes evaluating whether ratcheting up delivery prices for high-profile members such as Zuckerberg helps ensure that only messages truly of interest get to inboxes.
The Facebook messaging system was billed as being designed to deflect seemingly unwanted correspondence into an "other" folder that can be ignored.
Facebook said it wanted to determine whether adding a "financial signal" improves its formula for delivering "relevant and useful" messages to members' inboxes.
Facebook already uses social cues, such as connections between friends, and algorithms that identify spam messages.
Dabbling with getting people to pay to connect with Facebook members comes as the social network strives to tap the potential to make money from its membership base of more than a billion people.