SSO has become widely accessible and easy for small teams and startups to implement (it is baked in to many of the google/microsoft365 plans at this point). It also significantly increases security and compliance while decreasing administrative burden. As such, I would like to ask for SSO to be available outside of the Enterprise plan. Ideally, it would be a free offering, but it would be reasonable to charge a small amount per month per user in addition to the base fee.
For more information on why SSO should not be an enterprise only feature, please see the following articles: