Facebook announced a test this week (they don't typically announce tests), which lets users pay a small fee ($1 according to reports) to ensure that their messages get delivered to users' inboxes.
As you may know, Facebook previously launched the "Other Folder," which was designed as a place for less important or relevant messages to go, so the stuff people really want will be prioritized. Unfortunately, as Facebook points out, some users have complained that they're missing out on messages they'd like to be receiving, as they're buried in the "other" folder, which for all intents and purposes, might as well be considered the spam folder.
Here's the relevant section of Facebook's announcement:
Today we’re starting a small experiment to test the usefulness of economic signals to determine relevance. This test will give a small number of people the option to pay to have a message routed to the Inbox rather than the Other folder of a recipient that they are not connected with.
Several commentators and researchers have noted that imposing a financial cost on the sender may be the most effective way to discourage unwanted messages and facilitate delivery of messages that are relevant and useful.
This test is designed to address situations where neither social nor algorithmic signals are sufficient. For example, if you want to send a message to someone you heard speak at an event but are not friends with, or if you want to message someone about a job opportunity, you can use this feature to reach their Inbox. For the receiver, this test allows them to hear from people who have an important message to send them.
The feature is only available in the U.S. for a small number of people.