Access pricing is based on the number of users and the choice of identity provider (IdP). There are two plans: Basic and Premium. The basic plan offers support for social IdPs such as Facebook or Google whereas the Premium plan offers support for enterprise IdPs such as Okta, and G-suite. A complete list of features by plan as well as answers to frequently asked questions can be seen here.
Your Access plan is shared across zones in your account. You should purchase the number of seats you expect to need for all zones. The Access pricing calculator will help you estimate your price and select your plan based on the identity provider/s you need and the number of seats you expect to use.