One plan per organization, scaled to how many events you run and how many people need seats. Annual billing saves roughly two months against paying monthly.
A single department running its own home schedule.
Multiple event types, more people to coordinate, SMS reminders.
A conference office or multi-venue operator standardizing across sites.
Every organization starts on a trial. Plans and usage are configurable per organization in Settings once you're in — see it for yourself in the live tour.