Portal pricing is based on number of "seats." Every user of your portal requires 1 seat.
An Afterpattern portal allows you to package your apps into an online dashboard (a "portal") where others can make accounts, use your apps, and access their data.
When someone makes an account in your portal, they are taking up 1 seat.
Your Afterpattern subscription comes with a certain number of portal seats (see pricing page for details). If your Afterpattern subscription does not provide any portal seats, or you have used up all available seats, each extra seat costs $5 / month.
The Enterprise plan ($360 / month paid annually) provides you with 500 portal seats. If you want more than 500 portal seats, you can purchase up to 3 levels of add-ons.
Here is a breakdown of all Afterpattern plans + add-ons, the number of seats each provides, and the monthly cost per seat: