Time is money, and apparently, Facebook (NASDAQ:FB) CEO Mark Zuckerberg’s time is worth a lot of money.

Facebook recently put out a message to some users that requests $100 if you want to send him an email. And there’s no guarantee Zuck will even read it.

Zuckerberg isn’t out for petty cash, though. No, Facebook is experimenting with a new service for marketers — the system would require users to pay a fee to send a message to someone not on their friends list.

So far, the likely price point appears to be $1 per message. But Facebook is taking the scientific approach and exploring other prices.

Investors should look at this as promising for Facebook, in that it should better monetize the company’s massive user base — after all, a dollar or two per message and a billion people to work with can definitely add up.