For more details, see New Workplace Product Plans | Workplace blog
"Up to now, Facebook has taken a very simple approach to how it charges for Workplace, unique not just because of it being a paid service (unlike Facebook itself, which is free), but for how it modeled its pricing on the basic building block of Facebook-the-consumer product: a basic version was free, with an enhanced premium edition costing a flat $3 per active user, per month.Workplace, Facebook’s service for business teams, is raising its prices for the first time since launch | TechCrunch
In September, that will change. The standard (basic) tier is getting rebranded as Workplace Essential, and will still be free to use. Meanwhile, the premium tier is being renamed Workplace Advanced and getting charged $4 per person, per month. And Facebook is introducing a new tier, Workplace Enterprise, which will be charged at $8 per person, per month, and will come with a new set of services specifically around guaranteed, quicker support and first-look access at new features. (Those who are already customers have the option of being grandfathered for a year, the company said, before switching to a new plan.)"